bryan88 wrote:What caused the $100 million museum's approval and construction to take 12 years was a combination of the complexity of the financing requirements and the opposition of several small but vocal constituencies.
A)What caused
B)What has caused
C)The thing that caused
D)That which caused
E)Causing
A - "What caused the $100 million museum's approval and construction to take 12 years" IS THE SUBJECT...and matches with the verb WAS
B - HAS CAUSED (wrong tense). The causing is already over and therefore we require past tense
C - THE THING...WAS
A COMBINATION OF..AND THE OPPOSITION OF.. (IMO parts in bold is the logical subject and therefore we require WERE)
D - "THAT (WHICH CAUSED...12 YEARS) WAS A ...". Main clause is THAT WAS A COMBINATION OF ...(what DOES THAT REFERS TO); (2) in the relative clause WHICH refering to THAT, but since we do not have clarity on THAT, we cannot say what does WHICH refer
E - we do not what is subject now
IMO
A