Free Test Prep GRE-Verbal-Reasoning Exam Questions

The amount of bone in the elderly ske|eton—a key determinant in its susceptibility to fractures-is believed to be a function of two major factors. The first is the peak amount of bone mass attained, determined to a large extent by genetic inheritance. The marked effect of gender is obvious: Elderly men experience only one-half as many hip fractures per capita as elderly women. But also, African- American women have a lower incidence of osteoporotic fractures than Caucasian women. Other important variables include diet, exposure to sunlight, and physical actMty. The second major factor is the rate of bone loss after peak bone mass has been attained. While many of the variables that affect peak bone mass also affect rates of bone loss, additional factors influencing bone loss include physiological stresses such as pregnancy and lactation. It is hormonal status, however, refilected primarily by estrogen and progesterone levels, that may exert the greatest effect on rates of decline in skeletal mass. It can be inferred from the passage that the peak amount of bone mass in women

The Andean cordillera is made up of many inten/voven mountain ranges, which include high intermontane plateaus, basins, and valleys. The Northern Andes contain several broad ecosystems falling into four altitudinal belts. Its northern subregion is distinguished by higher humidity and by greater climatic symmetry between eastern and western flanks. The Central Andes are characterized by a succession of agricultural zones with varied climatic conditions along the mountains’ flanks and by large, highaltitude plateaus, variously called puna or altiplano, which do not occur in the Northern Andes. The soil fertility of the northern altiplano is generally good. The western Central Andean ranges are relatively arid with desert-like soils, whereas the eastern ranges are more humid and have more diverse soils. The eastern slopes of the Central Andes in many ways are similar to the wet forests of the Northern Andes. Unlike the Northern Andes, however, these slopes have a dry season. In regions of gentle topography, such as the Amazon basin, regional climatic variation can be determined from a few widely spaced measurements. Regional projections in the Andean cordillera are quite difficult by comparison. For example, while air temperature generally decreases with increasing altitude, variability of mountain topography can produce much lower than expected air temperatures. Nevertheless, some general climatic patterns are discernible. For example, with increasing distance south of the equator the seasonality of precipitation increases, whereas the total annual amount generally decreases. Humidity commonly increases with increasing altitude, but only to some intermediate altitude, above which it declines. The variability of mountain terrain also affects precipitation, such that conditions of extreme wetness and aridity may exist in close proximity. Related to this temperature gradient is a pattern of ater rainfall at the valley heads, and less rain at lower altitudes, resulting in part from mountain rainshadow effect. The weather patterns of the Andean cordillera and Amazon basin in general refilect movements of highand low-pressure cells associated with the Intertropical Convergence Zone, a low-pressure trough that moves further north and south on a seasonal basis. Precipitation is high throughout the year in the highlands and on the coast in the Northern Andes. Coastal aridity increases south of central Ecuador, culminating in the Atacama desert of northern Chile. In the Central Andes, highland precipitation is seasonal, and amounts are approximately half those measured in the Northern Andes. The aridity of the Central Andean coastal zone is the result of the drying effect of the cold Pacific Humboldt current and the southern Pacific high-pressure cell. lV|uch of the southern portion of the Central Andes in BolMa is also arid. The dry season causes soil moisture deficits and diminished stream flow part of each year. According to the passage, the northern part of the high-altitude plateaus is characterized by which of the following?

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The main advantage of inertial guidance systems in modern aircraft, spacecraft, and submarines is that they are and are able to function without data.