The idea of fish being able to produce electricity strong enough to light a lamp is almost

问题补充：

The idea of fish being able to produce electricity strong enough to light a lamp is almost unbelievable, several kinds of fish are really able to do this.

A. therefore

B. and

C. then

D. but

答案：

A. therefore

B. and

C. then

(答案→)D. but

解析：连词辨析。A.因此 B.和，并且 C.那么，然后；D.但是。句意：鱼能够产生的电流足够点亮一盏灯的想法，是令人难以置信的，但是有几种与确实能够做到这一点。故选D。