Acceleration is the rate of change of velocity, and velocity is the change in displacement over the change in time so the answer would be A.
The wavelength would be 2.980044314115. Reduced it would be 2.980 or just 2.98.
Water holds in heat very well. Keep the temperature more steady and average. The areas around the water will also have a less variant change in temperature as a result. This property of water is known as high specific heat.