A：swims
B：swim
C：swimming
— I haven't ________ Mike for a long time.
—I think maybe he is too busy to write to you.
家兔的主要特征是体表____ ；用____ 呼吸；心脏有两心房和____ 心室；体温____ ；繁殖后代为____ 。
下列有关命题的说法正确的是（ ）
