— At seven o'clock every morning. He likes his job, so he's _______ late.
A:usually
B:always
C:never
D:too
画出下面图形的展开图.(两种)
I _______ to you as soon as I get there.
近年来,抗生素的滥用致使很多致病细菌具有一定的耐药性.根据达尔文的进化论分析,耐药细菌越来越多的主要原因是( )
现有1000个氨基酸,其中氨基有1020个,羧基有1050个,则由此合成的4条多肽链中共有肽键、氨基、羧基的数是 ( )