One arm of a U-shaped tube is connected to a gas tap, while the opposite arm is open to the air. The tube contains water with density $1000\ \text{kg m}^{-3}$, and the heights of the water level in both arms are indicated. Atmospheric pressure is $101\ \text{kPa}$. What is the pressure of the gas at the gas tap?
- A99 kPa
- B100 kPa
- C102 kPa
- D103 kPa