题目

What _______ the forest in our country in the last ten years.         A. has happened do B. is happened to    C. has happened at  D. is happening 答案：A下列离子方程式中，正确的是（　　） A、氨水与硫酸铝溶液反应：Al3++3OH-═Al（OH）3↓B、稀硫酸滴在铜片上：Cu+2H+═Cu2++H2↑C、氢氧化铝与盐酸反应：Al（OH）3+3H+═Al3++3H2OD、铜片插入硝酸银溶液中：Cu+Ag+═Cu2++Ag