胰岛是指————————————————————————————。
参考答案：由分布于胰腺外分泌部之间的一团内分泌细胞
Fierce as they are faced with pressure, the students remain ________ and try hard to achieve their goals. [ ]
A. conscious
B. optimistic
C. nfluential
D. competitive
当潮汐为分点潮时，潮汐现象表现为（）。
A．周日不等现象最显著
B．周日不等现象最小
C．半日不等现象最显著
D．半日不等现象最小
