The letters PTA _____ parent-teacher association.
A. stand for
B. call for
C. reach for
D. care for
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内部网关协议RIP 是一种广泛使用的基于(35) 的协议。RIP 规定一条通路上最多可包含的路由器数量是(36) 。
A. 1 个
B. 16 个
C. 15 个
D. 无数个
Although these bears are strong swimmers, they are no match for lightning swift seals in the water.
This is the last thing I would ever want to do.
线粒体是细胞内进行______的主要场所,其上带有多种酶,主要作用是参加______氧化反应、电子传递和能量转换。