What's the best present you have ever _____?[ ]
A. received
B. receives
C. receiving
答案:A
如图是低倍显微镜下观察到的根毛细胞图,则该细胞在载玻片上的放置状况是
按照所用气体不同,气体保护焊可以分为()和二氧化碳气体保护焊。