—It is very clean and beautiful _____ it is a bit small.
A:if
B:since
C:unless
D:although
如图中最后一秒的加速度为____ m/s2.
函数y=2cos2(x-π4)-1是( )
He is a strict teacher, but all the students like him. I don't know why.
在受精的鸡卵中,能发育成雏鸡的是( )