The possible long-term health risks to airline personnel who

[BTGmoderatorDC]

The possible long-term health risks to airline personnel who repeatedly cross multiple time zones has been a concern since the first jet transports went into service in the 1950s.

A) who repeatedly cross multiple time zones has been a concern since the first jet transports went
B) who are repeatedly crossing multiple time zones has been a concern since the first jet transports that went
C) who repeatedly cross multiple time zones have been a concern since the first jet transports went
D) repeatedly crossing multiple time zones has been a concern since the first jet transports went
E) repeatedly crossing multiple timezones have been a concern since the first jet transports going

OA C

Source: Gmat Prep

[ceilidh.erickson]

This question is testing SUBJECT-VERB agreement.

The subject of this sentence is RISKS:
The ... risks (to airline personnel (who ...)) has been a concern ...

The GMAT often puts long, distracting modifiers between the subject & the verb to confuse your ear. If you notice a split between SINGULAR v. PLURAL VERBS (e.g. "has been" v. "have been"), look for the subject, and ignore any nouns in modifying phrases or clauses.


A) who repeatedly cross multiple time zones has been a concern since the first jet transports went
- the subject "risks" requires a plural verb: "have been," etc.

B) who are repeatedly crossing multiple time zones has been a concern since the first jet transports that went
- the subject "risks" requires a plural verb: "have been," etc.
- "who are crossing" - we don't need a complex verb tense (present progressive) when a simple on (simple present) will do.

C) who repeatedly cross multiple time zones have been a concern since the first jet transports went
- correct!

D) repeatedly crossing multiple time zones has been a concern since the first jet transports went
- the subject "risks" requires a plural verb: "have been," etc.

E) repeatedly crossing multiple timezones have been a concern since the first jet transports going
- "since" sets up a clause, so it is best to say "since the first jets went." "... since the first jets going..." would be a phrase rather than a clause.

The answer is C.

[vietnam47]

if we see doing/to do, you have to give it tense and agent
crossing and going take "have been. this mean
have crossed repeatedly
transport which have going ...in 1950

repeatedly require simple tense. which is used for repeated action
in 1950 requires past simple, not present perfect.
choice e is gone