unmanned aerial vehicle是什么意思

The country has already sent up three unmanned spacecraft,the most recent at the end of lastMarch.
A.has beenlaunched B.having been launched
C.beinglaunched D.to be launched
我的问题是,这里直接用launched可不可以?为什么要用现在分词的被动,而不能直接用过去分词?

The country has already sent upthree unmanned spacecrafts, the most recent at the end of last March.

[ ]

A．has been launched B．having been launched C．being launched D．to be launched

关于非谓语动词的几点疑惑
The country has already sent up three unmanned spacecraft,the most recent ( ) at the end of last March
A .has been launched B.having been launched
为什么要加ING?
所以想问 have been done having been done To have done.有什么区别?
获知说,现在分词是表主动,那having加了个been不是变被动了吗
还有,什么情况下可以主动表被动啊

还是英语非谓语求帮助,
The country has already sent up three unmanned spacecraft ,the most recent __________at the end of last Marth
A has been launched
B having been launched
C being launched
D to be launched
为什么选B,我选的是A

The country has already sent up three unmanned spacecraft,the most recent ______at the end of last March .
A.has been launched
B.having been launched
C.being launched
D.to be launched
选B 解析上说此句前后句没连词,只有逗号是不能连接两个句子的,所以后边the most recent ______ at the end of last March就是独立主格的形式了,在句中做伴随状语

The country has already sent up three unmanned spacecrafts,the most recent at the
The country has already sent up three unmanned spacecrafts,the most recent -----at the end of last March.A has been launched B .having been launched C.being launched D to be launched

The idea is that the nation ______ an unmanned spacecraft to explore the planet first.
a.sent b.sends c.send d.must send
为什么

The country has already sent up three unmanned spacecraft ,the most recent (having been launched) at the end of last March.
括号内have为什么要加ing

The country has already sent up three unmanned spacecrafts, the most recent
若是语法填空题the most recent 后可否只用lunched 表完成和被动

1、The country has already sent up three unmanned spacecraft ,the most recent _____ at the end of last March.
A has been launched B having been launched 为什么啊 我觉得是A啊
2_____different life is today from ______it used to be ten years ago.
A How what B what that A 我选B 刚好反调 我郁闷 为什么啊
3 By serving others,a person focuses on someone other then himself or herself ,____can beivery eyeopening and rewarding.
填的是which 为什么不是who 先行词不是a person
4 Their goods are exchanged for such machinery and equiment_____we need tobuy abroad.
as 为什么不用that 是不是as指的是像前面提到的一类物品 而that 指的是前面提到的同一物品啊

跪求Study on the long-range marine cruise system of unmanned aerial vehicles是否被SCI和EI收录

Another unmanned spacecraft “Shenzhou Ⅱ”,___ China greets the 21st century,marks new progress
in the country's space program.
A for which
B from which
C in which
D with which

1.another unmanned spacecraft "shenzhou 2",_______china greets the 21st century,marks new progress in the century's space program.
a.for which b.from which c.in which d.with which
2.beijing *** puts more than 700 million yuan to increase its green space this year,_____ doubles the money provided last year.
a.as b.while c.that d.which
3.that passenger was very impolite to the conductor,_____of course,made things even worse.
a.who b.whom c.what d.which
4.helen is much more kind to her youngest child than to the others,of course,______makes the others unhappy.
a.who b.which c.she d.that
5.i'll never forget the days ______i lived in the country with the farmers,_____has a great effect on my life.
a.that; which b.when; which c.which; that
d.when; who
从2~5题都是选which.我不是很明白为什么.
第一题是不清楚用哪个词组...

the country has already sent up three unmanned spacecraft,the most recent__at the end of the march
has been launched having been launched
why?