akash singhal wrote:In the major cities of industrialized countries at the end of the nineteenth century, important public places such as theaters, restaurants, shops, and banks had installed electric lighting, but electricity was in less than one percent of homes, where lighting was still provided mainly by candles or gas.

(A) electricity was in less than one percent of homes, where lighting was still
(B) electricity was in less than one percent of homes and lighting still
(C) there were less than one percent of homes with electricity, where lighting was still being
(D) there was less than one percent of homes that had electricity, having lighting that was still
(E) less than one percent of homes had electricity, where lighting had still been

A conjunction such as and must serve to connect PARALLEL FORMS.
B: electricity was...and lighting still provided mainly by candles
Here, the portions in red are not parallel forms.
electricity was = subject + verb.
lighting still provided mainly by candles = noun + modifier.
Eliminate B.

COMMA + where must be immediately preceded by a PHYSICAL PLACE.
C and E: electricity, where
Here, where seems to refer to electricity, which is not a physical place.
Eliminate C and E.

COMMA + VERBing serves to express an action that happens CONCURRENTLY WITH or AS A RESULT OF the nearest preceding action.
D: homes that had electricity, having lighting that was still provided mainly by candles
Here, COMMA + having implies that homes were HAVING lighting provided mainly by candles at the same time as they HAD electricity.
These meanings contradict each other.
Eliminate D.

The correct answer is A.