With time and public support, they should be successful.

What correction should be made to this sentence?
1) change the spelling of support to suport
2) replace they with one
3) change should be to should have been
4) change the spelling of successful to sucessful
5) no correction is necesarry

I think its 3, is that correct?

No. Successful is spelled correctly.

So the answer should be the 5?

Yes, 5.

Yes, you are correct. The correction that should be made to the sentence is to change "should be" to "should have been." The correct sentence would be: "With time and public support, they should have been successful." This correction changes the verb tense from present to past, indicating that the success was expected in the past, but may not have been achieved.