The most effective substitution for the phrase "This was probably due to" in this sentence is - <u>This discrepancy can be attributed in part to</u>. The correct option is Option C.
<u>Explanation:</u>
This particular sentence from the excerpt taken from the 2000 California Census is a person’sopinion about the reason for a particular discrepancy.
In the sentence, someone is stating that something must have happened because of the high unemploymentrates in the timber-related industries in the year 2000 and thus, uses the phrase "This was probably due to” which indicates someone’s own thoughts about something. Due to this, option C fits as the bestsubstitution for this phrase.
