The correct passive form of the given sentence "Manu will tell her later" is She will be told later by Manu.

The active voice of the sentence is "Manu will tell her later." This sentence is in the simple future tense, which is used to describe an action that will happen in the future. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the past participle of the main verb. In this case, the subject of the active sentence is "she" and the main verb is "tell." The past participle of "tell" is "told." So, the passive form of the sentence is "She will be told later by Manu."

The other options are incorrect because:

• She will be tell later by Manu." This sentence uses the wrong form of the verb "tell." The correct form is "told."
• She will tell later by Manu." This sentence is in the active voice, not the passive voice.
• She will be tell later." This sentence is missing the word "by." The passive voice requires the agent, which is the person or thing that is doing the action, to be mentioned.
• She will be told later." This sentence does not have a subject. The passive voice requires a subject, which is the person or thing that is being acted upon.