Topic: Linkers or Connectors,

Best Answer Explained in Below-:

The phrase "It was difficult to see clearly----" sets up a need for a dependent clause that explains why visibility was poor.

Looking at the options:

A) "because the rain," - This option is incorrect because it suggests an incomplete thought; it lacks the proper verb phrase to connect clearly to the main clause.

B) "because raining," - This option is also incorrect as it is grammatically incomplete. "Raining" lacks a subject or auxiliary verb, making it sound awkward and informal.

C) "because it is raining," - While grammatically correct, this option doesn’t match the tense of the main clause. "It was difficult" is in the past tense, and switching to present tense ("it is raining") creates a tense inconsistency.

D) "because it was raining." - This is the correct answer. Both the main clause and this dependent clause are in the past tense, making the sentence cohesive and grammatically sound. It clearly indicates that the difficulty seeing occurred at the same time as the rain, helping the reader understand the relationship between the two events. Therefore, option D maintains clarity and tense consistency, making it the most suitable completion of the sentence.