✔ 最佳答案
The present perfect tense can be used here to denote present results of past actions. Since the actions are completed recently(=this morning),the words "just" and "already' are used."just" is used to mean the immediate past while "already" shows completion on leaving.
Gerund is a noun in the form of the present participle of a verb hit=hitting.
;"saw" and "hitting" are not two verbs in a sentence:-
Hence:-eg:-I have just seen 3 men hitting (=gerund) a child.
If you leave,then::-I have already seen their hitting (=gerund) a child.