My father was too . . . . . . . . to push open the heavy door.

timid
faint
feeble
faltering

The correct answer is: C. feeble

A feeble person is weak and frail. They may have difficulty moving or performing everyday tasks. They may also be easily tired.

Timid people are shy and nervous. They may be afraid to speak up or take risks.

Faint people are unconscious. They may have passed out due to low blood pressure, dehydration, or a medical condition.

Faltering people are hesitant or uncertain. They may be unsure of what to do or say.

In the given sentence, the speaker is describing their father as being too weak to push open the heavy door. This suggests that the father is feeble.