The two main criteria that the National Science Foundation (NSF) uses to evaluate grant proposals are

Intellectual merits and broader impacts.

Explanation:

In the evaluation process to grant proposals of researchers, the National Science Foundation ensures that they apply sufficient and logical criteria to determine what research or which researcher to award a grant.

NSF recognizes two priority considerations when agreeing on what and who to award a grant. The first criterion is the INTELLECTUAL MERIT of the project, this is based on whether the research advances current knowledge.

The second criterion is based on whether the research has BROADER IMPACTS, that is, its likely benefit and contribution to society at large.

Hence, the correct answer is Intellectual merit and broader impact