19) What is the negation of the sentence "Every student in 1st A has at least 2 cousins"?

(A) No student in 1st A has cousins

(B) all students in 1st A have one cousin

(C) at least one student in 1st A has only one cousin

(D) at least one student in 1st A has no cousins

(E) none of the above is the negation of the given sentence.
19) The answer is (E)

The negation of the sentence is "At least one student in class IA has at most one cousin." Note that between a sentence and its negation, one and only one is true. Sentences (A), (B), (C), (D) are not the negation of the sentence in the text, as, for example, if no student in class 1A has cousins, both the sentence in the text and (B) and (C) are false, while if all students in class IA have exactly one cousin, both the sentence in the text and (A) and (D) are false.