Explanation : 

Statement I: In January, in the Northern Hemisphere, the isotherms bend equatorward while crossing the landmasses, and poleward while crossing the oceans.

Isotherms are lines on a map that connect points of equal temperature. During January, it is winter in the Northern Hemisphere. Land cools down more rapidly and to a greater degree than water during winter. As a result, landmasses in the Northern Hemisphere become significantly colder than the oceans. This sharp decrease in temperature over land causes isotherms to bend sharply towards the south (equatorward) over continents, especially pronounced in areas like Europe and the Siberian plain.

Oceans have a higher heat capacity than land, meaning they absorb and release heat more slowly. Consequently, oceans retain heat longer and are relatively warmer than landmasses during winter. Warm ocean currents, such as the Gulf Stream and North Atlantic Drift, further contribute to making the Northern Atlantic Ocean warmer, causing isotherms to bend towards the north (poleward) over the oceans.

Therefore, Statement I is correct.

Statement II: In January, the air over the oceans is warmer than that over the landmasses in the Northern Hemisphere.

Land heats up and cools down more rapidly and to a greater degree than water. In January, which is winter in the Northern Hemisphere, landmasses cool down significantly, becoming much colder than the adjacent oceans. The air temperature over land fluctuates more because land changes its temperature much more rapidly than ocean water.

Water has a high specific heat capacity, meaning it takes more energy to change its temperature. This property allows oceans to store a large amount of heat and release it slowly, moderating the temperature of the overlying air. As a result, the air over oceans remains relatively warmer than the air over landmasses during the Northern Hemisphere winter.

Therefore, Statement II is correct.

Relationship between Statement I and Statement II:

The differential heating and cooling of land and water (Statement II) is the primary reason for the bending of isotherms (Statement I). Because land cools more rapidly and becomes colder than the oceans in winter, the isotherms dip southward (equatorward) over land to connect points of equal, colder temperatures. Conversely, because oceans retain heat and are warmer, the isotherms bend northward (poleward) over oceans to connect points of equal, warmer temperatures. This direct relationship indicates that Statement II explains Statement I.

Correct Answer : (a)