题目

At school, some students are active ________ some are shy, yet they can be friends with one another. A . while B . although C . since 答案：A做完试验后，对于用过的废酸，你认为正确的处理方法是                             （     ）    A.拿出实验室                          B.留在试验台上，准备下次实验用 C.倒入指定的废液缸中                  D.放回试剂瓶