Answer : B

Here, 'what' is more appropriate than 'whatever'.

'Whatever' is generally used as an indefinite - i.e., to refer to potential things/events that haven't been realized yet.
“You can get whatever you might need for your project at the drugstore.” >You don't yet know what you need.
“You can get what you need for your project at the drugstore.” >You (and even the speaker) know exactly what you need.
It is logical that 'what he lacked...' is a KNOWN quantity, so 'what' must be used here instead of 'whatever'.
Therefore, C, D, and E are incorrect because of the use of “whatever”.

A: Baker was… not gifted(active voice), but the conductor felt what was lacking in his(passive voice) technical skill was more than made up by the passion with which he played the music.
The sentence opens with active voice and then changes to passive. Hence, incorrect

B: “Baker was… not gifted, but the conductor felt what he lacked(active voice)… was more than made up by the passion with which he played…” B is the best choice.

Hit Kudos

Bunuel can you please post official explanation for this question or can some one explain why whatever is wrong?