About a grammar

[Anonymous]

in toefl test ,there is a question like this:


Until the eighteenth century, charcoal was______ used in blast furnaces, as well as in glassmaking, blacksmithing, and metalworking.
(A) what the chief fuel
(B) the chief fuel that
(C) the chief fuel was
(D) the chief fuel

the current answer is D.

can you tell me why?I thought is B.

[Tdol]

If you use B), you'll have to say 'that was used'.

[RonBee]

Say the correct answer is D. If you say the current answer that suggests it might somehow change.

:wink: