The upset mother thought to herself, “If only I ______ what's going on in my little boy's head right now.”
A:know
B:knew
C:have known
D:had known
38÷5 4÷59 715÷1 1÷72520÷45 1213÷3 34÷13 1749÷1
如图所示的每个图的下面是小明分别记录的测量结果.其中记录正确的是( )
如图所示,已知OA⊥OB,OC⊥OD,则图中∠1和∠2的关系是( )