GWD30-20 of which type怎么理解

kevinjpcn

GWD30-20

[size=1em]Researchers have announced that the magnetic fields emitted by one manufacturer’s security surveillance system, of which type there are 200,000 worldwide, can interfere with pacemakers and that this interaction can bring on missed or irregular heartbeats, nausea, breathlessness, dizziness, and even fainting. [size=1em] A  of which type there are 200,000 worldwide, can interfere with pacemakers and that B  of which, worldwide, there are 200,000 of that type, and which can interfere with pacemakers, and C  of which type there are 200,000 worldwide, they can interfere with pacemakers and D  200,000 of which type exist worldwide, interfering with pacemakers, and E  200,000 of that type existing worldwide and can interfere with pacemakers, and

这道题答案是A。请问of which type 的which指代谁？这是什么用法啊。怎么翻译啊。
麻烦牛人致电。

bejamin1111

which就近指代security surveillance system，这句话的意思是there are 200,000 security surveillance systems worldwide.

kiwifoodtown

LS正解。