The inventor of the first practical helicopter in the world was (Igor Ivanovich Sikorsky).
The plant representing peace is (olive branch)
Four light years is a unit.
5 1 1.9 is the National Fire Day.
Low carbon is mainly to reduce gas emissions.
Animals that sleep in summer are (sea cucumber) and (lungfish).
Knowledge is power is a famous saying of Francis Bacon.
The lake in Hunan and Hubei is Dongting Lake.
1 People heard the sound of fireworks before or after seeing them.
The most beautiful red tourist attraction in China is Jinggangshan.
The correct posture when sleeping is (lying with legs bent to the right)