Which sentence correctly uses an objective case pronoun
shani and me sang a duet at a concert.
them told sean about the fundraiser.
will you and her eat dinner with holly.
tell victor and him the truth.

Tell Victor and him the truth. This is the correct option.

The underlined word is the pronoun in the objective case. The verb "to tell" is followed by these pronouns. Someone is giving a person an order; to tell Victor and another man (him) the truth. The speaker and the listener must know who "him" is. They could have mentioned him before in the dialogue.

These options are not right:

-Shani and me sang a duet at a concert. ( The undelined word should be replaced by I. Pronouns in the agentive case are needed here. )

-Them told sean about the fundraiser. (  This sentence is wrong.They shoudl replace the underlined word. The agentive case is needed.)

-Will you and her eat dinner with Holly? ( Her is wrongly used. The speaker is asking a second person to do something. The message is addressed to "you". This sort of requests never address a third person. The correct version should be: Will you and your sister eat dinner with Holly?)

resents dr jekyll

explanation:

that is the answer

can i see the painting?