Answer: c. time of year.
Explanation:
The surface temperature of the ocean varies with the latitude and time of the year. The Earth revolves around Sun. Due to its tilt, seasons exist. The hemisphere which is faces sun has summer and the hemisphere which points away has winters. In summers, the surface temperate of the oceans rises and in winters it drops. It depends on the location of the ocean -in which zone it lies. The average temperature of oceans lying in the equatorial zone is greater than the ones in the temperate zone.
Thus, the ocean's surface temperature depends upon the latitude and time of the year.