C

The eighth US President was Martin Van Buren.

When discussing the fraction, it's lower case.

When discussing the grade, it's upper case.

Saturn

Yes. It can kill them in an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth of an eighth ofan eighth of an eighth of an eighth of an eighth of a millisecond.