The skin, an ________ part of your body and its largest organ, ________ as a barrier against diseases.
A:vital; acting
B:vital; acts
C:essential; acting
D:essential; acts
①相信自己能成功②遇到难题决不放弃 ③专心致志做题④能有效利用周边同学
下列叙述正确的是()