To get 'approval' means to receive endorsement, support, or permission from others. Option A correctly completes this definition. Options B, C, and D don't fit - getting 'questions', 'challenge', or 'evidence' doesn't mean receiving endorsement or support.
To "get approval" means to receive official agreement, endorsement, or support from others for a plan or action. Words like "questions," "challenge," and "evidence" describe scrutiny or proof, not the act of gaining backing.