China is a country that has made great ____(contribute) to mankind in history.
①若∠1=∠3,则AD∥BC;
②若AD∥BC,则∠1=∠2=∠3;
③若∠1=∠3,AD∥BC,则∠1=∠2;
④若∠C+∠3+∠4=180°,则AD∥BC.
— What a heavy rain! Will it last long?
— _______. We're getting into the rainy season now.