In which sentence does the verb number need to be changed in order to agree with the number of the subject?

a. my aunt and uncle usually sends me a picture postcard when they travel.

b. either samuel or kevin is doing his next report on careers in biology.

c. art, math, and science need to be studied by architecture students.

d. the oak tree and the maple tree in the front yard shade the porch.

A. My aunt and uncle usually sends me a picture postcard when they travel.

Explanation:

The subject is My aunt and uncle. This phrase can be replaced with the pronoun they because we have two people here who send me a postcard. So  the verb number needs to be changed in order to agree with the number of the subject: it should be send, not sends.  

In other words, use a plural verb with two or more subjects when they are connected by and.    

he chooses to climb mount everest and decided not to any more due to the 1,000s of people making a line on the mountion

explanation:

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