Identify the segment that contains a grammatical error. If there is no error, select ‘No error’.
If Tom was here, / he could have / solved the issue.

Correct option is C

Option (c) contains an error.
Error Explanation: In conditional sentences describing unreal past situations, we use “If + past perfect”. So, "If Tom was here" should be "If Tom had been here".
Correct sentence: If Tom had been here, he could have solved the issue.
Grammatical rule used: Third conditional structure:
Structure: If + past perfect, subject + could have + V3
Example: If I had studied harder, I could have passed the exam.
Information Booster: “Was” is acceptable with “If” only in second conditional (present unreal), not in third conditional (past unreal).