Answer:
"Zebras sleep standing up."
Explanation:
The rest are all opinions, "Zebras sleep standing up" can be proven with facts.
i'm afraid the previous answer is incorrect.
so you understand the concept, i will explain why it is choice A.
present participle: a verb used as an adjective to describe a noun
choice A: barking is an adjective acting as a verb
choice B: a gerund is only used as a noun
choice C: running is a verb in the sentence, not an adjective
choice D: running in the sentence is not a past participle
:)
First sentence, due to the above questions
The answer for your question would be D