语法大全 679.Temporary-employment agencies benefit not only from the increasing demand for clerical workers but also the higher profits made when highly paid professionals are placed, requests for whom have increased in the recent wave of corporate takeovers. (A) the higher profits made when highly paid professionals are placed, requests for whom (B) the higher profits that are made in the placement of highly paid professionals, requests for whom (C) from the requests for highly paid professionals, who make higher profits for the agencies when placed and whose requests (D) from highly paid professionals, whose placement makes higher profits for the agencies and whose requests(E) (E) from the higher profits made in placing highly paid professionals, requests for whom 我选了C。。不应该是benefit not only from demand for... but also from requests for...吗? 677.Sunspots, vortices of gas associated with strong electromagnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun’s poles or equator. (A) are visible as dark spots on the surface of the Sun but have never been sighted on (B) are visible as dark spots that never have been sighted on the surface of the Sun (C) appear on the surface of the Sun as dark spots although never sighted at (D) appear as dark spots on the surface of the Sun, although never having been sighted at(C) (E) appear as dark spots on the Sun’s surface, which have never been sighted on 为什么不能选A?
677.Sunspots, vortices of gas associated with strong electromagnetic activity, are visible as dark spots on the surface of the Sun but have never been sighted on the Sun’s poles or equator. (A) are visible as dark spots on the surface of the Sun but have never been sighted on (B) are visible as dark spots that never have been sighted on the surface of the Sun (C) appear on the surface of the Sun as dark spots although never sighted at (D) appear as dark spots on the surface of the Sun, although never having been sighted at(C) (E) appear as dark spots on the Sun’s surface, which have never been sighted on 为什么不能选A?