1. Q019 Brad will burp on command ____ cannot flare his nostrils.
The right choice is ...
but
but,
, but
; but
Well done! The conjunction but is connecting two verbs, will burp and can flare, not two main clauses. No punctuation is necessary.
When you use a comma with the conjunction but, it almost always comes before the but, not after.
Use a comma before the conjunction but when you have a main clause on both sides: Brad will burp on command, but he cannot flare his nostrils.
When the conjunction but requires punctuation, you will almost always need a comma, not a semicolon.