题目

Two birds(鸟) are _______________ and an apple is _______________. A . in the tree; in the tree B . on the tree; on the tree C . in the tree; on the tree D . on the tree; in the tree 答案：C下列运算正确的是 [     ]A．2a2+a=3a3B．（﹣x2）3÷（﹣x3）2=﹣1C．（﹣a）3a2=﹣a6D．﹣2a﹣3=