Question

MUCH MORE experimental data ARE required BEFORE we can accept THIS THEORY. or NO ERROR

which one of the caps is worng?? and whyy??

Answer 1

Since you can use "data" with either a singular or plural verb, I'd replace "are" with "is."
http://www.answers.com/data

Or ... since you can use "data" with either a singular or plural verb, you could mark it "no error."

Others may have different ideas.