Choose the grammatically correct sentence.

The correct answer is Option (3) → Grapes cannot be gathered from thistles.

Passive voice with a modal:

• Grapes do not gather anything; they are gathered by people, so the sentence must be in the passive.
• With a modal the passive is modal + be + past participle: cannot + be + gathered.
• The proverb means that good things cannot come from a bad source.
  Example: This work cannot be finished in a day.

Why the Other Options are Incorrect?

Option 1: Grapes cannot gathered from thistles. — Incorrect. A modal is followed by the base form or by "be"; "cannot gathered" leaves out "be".

Option 2: Grapes could not gathered from thistles. — Incorrect. The same mistake: "be" is missing after "could not".

Option 4: Grapes cannot gather from thistles. — Incorrect. It is in the active voice and makes the grapes the doers, which makes no sense.

Contrast: in the active "cannot gather" the grapes would do the gathering; in the passive "cannot be gathered" they receive the action.