What is the rule of follow-on in Test cricket?

ٹیسٹ کرکٹ میں فالو آن کا قاعدہ کیا ہے؟

The team batting second can be asked to bat again immediately if they trail by a large margin after the first innings.

The team batting first can skip their second innings.

The match ends if the team batting second scores fewer runs.

None of these

The follow-on is enforced to make the team batting second bat again without the other team batting a second time if the lead is big.

This rule speeds up the game to try for a result.