You must leave now ________ you can meet your mother at the airport on time.
A:only if
B:only
C:so that
D:so
已知玉米籽粒黄色对红色为显性,非甜对甜为显性。纯合的黄色非甜玉米与红色甜玉米杂交得到F1,F1自交或测交,预期结果不正确的是( )
下列关于质点的说法中正确的是( )