单项选择题Directions:Please choose the best answer from the following 4 choices, and fill in the blanks with the corresponding letter. We were early for our appointment, so we _____ at a bookstore. A、race against time B、time has come C、time out D、kill time
单项选择题人首先必须活着,然后才能做别的事情。
判断题继电器一般用来直接控制有较大电流的主电路。
单项选择题转向器是转向系统中减速增扭的传动装置。 A、正确 B、错误
不定项选择高尔基复合体的发生来源于内质网和核膜