发射的类型有离心式发射、向心式发射、同心式发射和多心式发射等。
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以一个焦点为中心,层层环绕发射称为( )
A. 中心式发射
B. 同心式发射
C. 旋转式发射
D. 螺旋式发射
[音频]1
A. Looking for a job.
B. Traveling abroad.
C. Writing a term paper.
D. Working on a project.
2
A. Do some shopping.
B. Watch a football match.
C. Go fishing.
D. Visit their friends.
[音频]3
A. Sales Manager.
B. Marketing Manager.
C. Project Manager.
D. Research Manager.