Which sentence contains an inappropriate shift in tense?

a.
i am reading a poem that was written thousands of years ago.

b.
i finished painting the fence, but barbara is still repairing the gate.

c.
hummingbirds are hovering over the geraniums while caterpillars munched leaves.
i its c but iam not sure

Ivansanger rainsfordgeneral zaroffwhitneyadventurous hunter; calm and composed; considers himself a realist; new yorker; veteran of world war ia hunter; sympathetic to the plight of voiceless, defenseless animals; cautiouscossack; mute; formidable physical stature; wears a black uniform; used to whip prisoners for the great white czarcossack; aristocrat; has sharp, pointed teeth and red lips; devoid of humanity and emotion