Which of the following collections of letters will look the same in the mirror ?

AOVIVOA

1. OSMIHOM: Read from left to right: O-S-M-I-H-O-M. Read from right to left: M-O-H-I-M-S-O. Not the same.

2. VHRTRVH: Read from left to right: V-H-R-T-R-V-H. Read from right to left: H-V-R-T-H-V. Not the same.

3. HIMOSTA: Read from left to right: H-I-M-O-S-T-A. Read from right to left: A-T-S-O-M-I-H. Not the same.

4. AOVIVOA: Read from left to right: A-O-V-I-V-O-A. Read from right to left: A-O-V-I-V-O-A. Ah, this one is the same! 

Thus, "AOVIVOA" is correct.