A:Not known how to
B:Unknown what to do to
C:His knowing not how to
D:His not knowing how to
在下面的图形中,分别过A点画BC的垂线.
选择正确的解释。(只填序号)
挺:①笔直 ②伸直或凸出 ③很 ④量词
一挺机枪____ 昂首挺胸____
挺美的____ 笔挺____