In theory, international civil servants at the united nations are prohibited from continuing to draw salaries from their own governements; in practice, however, some governements merely substitute living allowances for their employee's paychecks, assigned by them to the united nations.
(B) for the paychecks of their employees who have been assigned (C) for the paychecks of their employees, having been assigned
The correct choice is B. The explanation for C is "Having been assigned casts doubt on whether the employees are still assigned to the united nations." I just can not understand this explanation. Why Having been assigned casts doubt on whether the employees are still assigned to the united nations
however, in (B) the author also used "have been". And I guess the author intend to mean that the action is ongoing. So I can not tell any differences between B and C.
