The correct answer is: A. like
The verb “like” is used to express a feeling of enjoyment or pleasure. In the sentence “In cold climates people like sitting in the sun,” the speaker is expressing the idea that people in cold climates enjoy sitting in the sun.
The verb “likes” is the third person singular form of the verb “like.” It is used to express the idea that a specific person enjoys something. In the sentence “John likes sitting in the sun,” the speaker is expressing the idea that John enjoys sitting in the sun.
The verb “are liking” is the present progressive form of the verb “like.” It is used to express the idea that someone is currently enjoying something. In the sentence “People are liking sitting in the sun,” the speaker is expressing the idea that people are currently enjoying sitting in the sun.
The verb “do like” is the emphatic form of the verb “like.” It is used to express the idea that someone definitely enjoys something. In the sentence “I do like sitting in the sun,” the speaker is expressing the idea that they definitely enjoy sitting in the sun.
In the sentence “In cold climates people like sitting in the sun,” the speaker is expressing a general idea about people in cold climates. They are not talking about a specific person or a specific time. Therefore, the verb “like” is the most appropriate option.