题目

 I didn’t know if it ______ tomorrow. If it ________, I will stay at home. A. will rain; rains          B. rains; will rain C. will rain; will rain       D. rains; rains    答案：A已知点O(0,0)，A(0，b)，B(a，a3)．若△OAB为直角三角形，则必有(　　)．A．b＝a3B．b＝a3＋C．(b－a3) ＝0D．|b－a3|＋＝0