Answer is option A: The oceans are becoming warmer because the atmosphere trapped more heat between 1990 and 2010.
As the greenhouse gases emission increased because of the development activities by the human race. These gases stay in the atmosphere and their ability to trap the sunlight and the heat radiated from the earth surface is very high. Due to this reason, the temperature of the atmosphere keeps increasing as the emissions keeps on rising during this period. The top surface is in direct contact with the atmosphere. Hence, the heat from the atmosphere heats up the ocean surface due to which the average surface temperature kept on rising from 1990 to 2010.
