It still puzzles today’s scientists ______ some mammals produce their young ______ others lay eggs to produce their offspring( 后代)

A．that; while

B．why; while

C．how; when

D．what; as

（）的风切变情况导致空速增大。

A.增大顺风

B.顺风和逆风都增大

C.减小顺风，增大逆风

D.减小逆风