1742. Much of Tibet lies at altitudes over 18,000 feet where the pressure is about 500 mb. At such altitudes, the Tibetans are above roughly:

A. 10% of the air molecules in the atmosphere
B. 25% of the air molecules in the atmosphere
C. 50% of the air molecules in the atmosphere
D. 75% of the air molecules in the atmosphere
✅ The correct answer is option C.
Much of Tibet lies at altitudes over 18,000 feet where the pressure is about 500 mb. At such altitudes, the Tibetans are above roughly 50% of the air molecules in the atmosphere.

1746. Two objects, A and B, have the same mass but the specific heat of A is larger than B. If both objects absorb equal amounts of energy,

A. A will become warmer than B
B. B will become warmer than A
C. Both A and B will warm at the same rate
D. A will get warmer, but B will get colder
✅ The correct answer is option B.
B will become warmer than A.

1747. In ecological succession from pioneer to climax community, the biomass shall

A. decrease
B. no relation
C. increase and then decrease
D. increase continuously
✅ The correct answer is option D.
When the community moved from a pioneer community to the climax community, the biomass will increase. This will increase the biomass because the number of organisms belonging to different species will also increase.

1749. All the genes of a population is called

A. gene pool
B. genome
C. gene bunch
D. gene population
✅ The correct answer is option A.
The Collective Set of Alleles in a Population Is Its Gene Pool. The fact that genes exist in alternate forms, called alleles, forms the basis for the study of population genetics. Populations are made up of members of the same species that interbreed.