Which sentence correctly uses parallel structure?

1.the boss wants to know who can take the late shift tonight, open tomorrow 2.morning, and who can work on the holiday.
3.the boss wants to know who wants the late shift tonight, who can open tomorrow morning, and if you will work on the holiday.
4.the boss wants to know who can take the late shift tonight, who can open tomorrow morning, and who can work on the holiday.

The correct answer is 4.

A parallel structure is a repetition of chosen grammatical form within a sentence. It shows that two or more ideas have the same level of importance. The usual way to join parallel structures is with the use of coordinating conjunctions such as 'and' or 'or'.

In the sentence number 4, the parallel structure is apparent by the use of the relative pronoun who that is repeated three times. This repetition makes the sentence easy to understand and it's grammatically correct. In a parallel structure, words should match not only in structure but also in tense.

4.The boss wants to know who can take the late shift tonight, who can open tomorrow morning, and who can work on the holiday. This is the correct option.

Parallel structure is applied when the same structure is used. The underlined clauses are the structure used in this way.   There are three thing the boss wants to know and these three things have got the same syntactic pattern, therefore the verb " to know" is followed by " who can " three times.

the pronoun reference replaces a noun, but you have to make sure there's no room for confusion.

in the first sentence "her" could be referring to shely or to the sister. the answer there is "shelly called her sister and told her about the new baby."

in the second sentence "it" could be referring to the roof or the floor. the answer there is "since the roof leaks on the family room floor, we need to repair the roof."