A. The weight of hydrogen is greater than the weight of the air.
B. The weight of hydrogen is equal to the weight of the air.
C. The weight of hydrogen is less than the weight of the air.
D. The surface of the balloon I smooth.
A. The weight of hydrogen is greater than the weight of the air.
B. The weight of hydrogen is equal to the weight of the air.
C. The weight of hydrogen is less than the weight of the air.
D. The surface of the balloon I smooth.