31) A & C

The best way to solve this question is by expressing the four statements as inequalities.

Anne is not older than Susan. So Anne is either younger or is of the same age as Susan.

A ≤ S

Susan is at least as old as Anne. So Susan is either older or is of the same age as Anne.

A ≤ S

Anne is not younger than Susan. So Anne is either older or is of the same age as Susan.

A ≥ S

__A – Correct__Anne is not older than Susan. So Anne is either younger or is of the same age as Susan.

A ≤ S

__B – Wrong__

Susan is younger than Anne.

A > S

__C – Correct__Susan is at least as old as Anne. So Susan is either older or is of the same age as Anne.

A ≤ S

__D – Correct__Anne is not younger than Susan. So Anne is either older or is of the same age as Susan.

A ≥ S

A and C have the same inequalities. So A & C are the answers.