— What did he _______ just now?— Sorry, I didn't catch his words. I_______ about something else.
A:speak; am thinking
B:talk; thought
C:say; was thinking
D:tell; have thought
图中有____条食物链,食物链的起始环节是____.
在探究“杠杆平衡条件”的实验中,杠杆上每格等距:
如图,在△ABC中,AB=BC,以AB为直径的⊙O交AC于点D,过D作直线DE垂直BC于F,且交BA的延长线于点E.
下列表述有误的一项是( )