Which of the following sentences is correctly punctuated? The new office phone, which has ten new dial features, will be installed on Tuesday. The new office phone, which has ten new dial features will be installed on Tuesday. The new office phone which has ten new dial features, will be installed on Tuesday.

As per the question, option A exemplifies a correctly punctuated sentence as it involves an appropriate use of comma(,) prior to and after the relative clause 'which has ten new dial features' that functions to modify or offer details about the noun(subject) 'The new office phone' in the sentence. The punctuation in the above statement is most appropriate as it clearly demonstrates the structural organization of the sentence by demarcating the non-restrictive clause(that adds description about the subject in the sentence) 'which has ten new dial features' from the principal meaning of the sentence('the new office phone will be installed today'). Therefore, option A is the correct answer.