The correct option is D d
The option that states the part with the error is the correct option.
These parts a, b and c form a complete sentence. 'Everybody' is the subject of this sentence. It is an indefinite pronoun that means 'every person'. Though it does not refer to a particular person, it is still singular, as it refers to every 'person'.
It performs the action 'has', followed by the subject complement 'their ups and downs'.
'Has' is a singular verb and agrees with the subject in number (singular).
Also, 'their' is a plural pronoun but an indefinite pronoun(everybody, anybody, somebody, they) does not tell us the gender of the person (her or him). Hence, in that case, we use 'their'.
So, these parts do not contain any error. They are grammatically correct and have a complete meaning.
Hence options A, B and C are all wrong answers, as they do not contain any error.
Option D is correct as it states: NO ERROR