SC - As a result of the medical advances

[thanghnvn]

As a result of the medical advances, many people that might at one time have died as children of such infections as diptheria, 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 are children, might at one time have died

Can the instructors explain what's wrong with option d?

because "who", not "that" is used to refer to persons in relative clause-according to gmat standard-, we can use "who" with and without comma to show restrictive and non restictive clause.

is that right?

[RonPurewal]

B, D, and E all have "who" without a preceding comma. There are no choices with comma + "who". Therefore, that consideration is a non-issue here.

[RonPurewal]

More importantly, GMAT SC does not test the difference between modifiers with commas and modifiers without commas.
(This is a highly conspicuous absence, since that difference is a very major"”"”and very common"”"”issue in English in general.)