Idiom from X to Y ..

[ramiy]

Studies of the human “sleep-wake cycle” have practical relevance for matters ranging from duty assignments in nuclear submarines and air-traffic control towers to the staff of shifts in 24-hour factories.
(A) to the staff of
(B) to those who staff
(C) to the staffing of
(D) and staffing

(E) and the staff of


DO explain the choices

[ludo_100]

Idiom range from X to Y...
IMO C...
maintains ||ism
Studies of the ....ranging from duty assignments ....to the staffing of....

[ramiy]

right boss !!

[hina_0611]

C for me too

[GMATBlr]

Imo C

[Fiver]

C is my pick.

The Idiom is 'Ranging from X and Y to Z', where X,Y & Z must be parallel.
Here X=Duty assignments, Y=Air-traffic control towers, both of which are nouns. Hence the following Z must also be a noun.
In C 'staffing' is a gerund and is preceeded by 'the' and followed by 'of': The conventional way to differentiate a gerund from a present participle.

[gettomanish]

C is the clear one.