Sentence Correction

121. As a result of medical advances, many people that might at one time have died as children of such infections as diphtheria, pneumonia, or rheumatic fever now live well into old age.
(A) that might at one time have died as children
(B) who might once have died in childhood
(C) that as children might once have died
(D) who in childhood might have at one time died
(E) who, when they were children, might at one time have died

IMO B

relative pronoun "who" should be used to refer to people. So, A & C are out. Among B, D & E only B retains the meaning of the sentence & is grammatically correct.

a. Use of that is wrong
b.Concise and conveys the intended meaning
c. Same error as A
d. Modifier problem - incorrect placement of "childhood" which is supposed to modify "died"
e. Too wordy.
Hence, b is the answer.