Jawaban:

(+) Sinta is cleaning the house now
(-) Sinta is not cleaning the house now
(?) Is sinta cleaning the house now?

Penjelasan:
Affirmative >> Negative
A negative word must be employed to change an affirmative sentence into a negative sentence. Remember that 'not' is only used with auxiliary verbs.

Affirmative >> Interrogative
1) An positive sentence is converted to a negative interrogative statement. If it's negative, it needs to be altered to a simple interrogative.

Examples:
He was very gentle. (Assertive)
Wasn't he very gentle? (Interrogative)
He is not a good person. (Assertive).
Is he a good person? (Interrogative)

2) If the sentence lacks an auxiliary verb, replace it with do/does/did. Alternatively, don't /Doesn't /didn't.

3) Who+ don't / doesn't / didn't replaces everyone/everyone/all