By offering lower prices and a menu of personal communications options, such as caller identification and voice mail, the new telecommunications company has not only captured customers from other phone companies but also forced them to offer competitive prices.

(A) has not only captured customers from other phone companies but also forced them

(B) has not only captured customers from other phone companies, but it also forced them

(C) has not only captured customers from other phone companies but also forced these companies

(D) not only has captured customers from other phone companies but also these companies have been forced

(E) not only captured customers from other phone companies, but it also has forced them

Option C. Has not only captured customers from other phone companies but also forced these companies

Explanation:

One of the common idiom used is "not only ... but also". As the option B and E includes the word "it" between "but also" hence these two are incorrect.

It is also worth noticing that it must place verb which comes just after "not only ... but also" and must be "captured ... forced" respectively. So the Option D is also incorrect because it doesn't places the verb in parallel position.

The option A uses the incorrect pronoun which is "them" because it doesn't highlights about whom it is addressing. Just look at the following sentence:

Has not only captured customers from other phone companies but also forced them. Here we don't know whom the pronoun "them" is addressing. It can be either customers or the companies. So there is a confusion. The correct pronoun must be "these companies" because it specify whom it is addressing.

Therefore, the answer is C.