When his car tyre … on the way, he did not know what to do.

Analyze the question: The sentence is "When his car tyre ......... on the way, he did not know what to do." We need the correct verb form for the gap. The main clause, "he did not know," is in the simple past.

Concept: When two past events are linked by "when," the tense depends on the sequence:

• If the first action was completed before the second, the past perfect (had + past participle) is often used.
• If the events happened almost together, with one triggering the other, both take the simple past.

Working through the options:

• A. has burst: present perfect. It clashes with the past tense "did not know," so it is wrong.
• B. had burst: past perfect. It is grammatically possible, and it would suggest the tyre had burst earlier and he was already dealing with it. That is a less natural reading here.
• C. bursted: "burst" is an irregular verb (burst, burst, burst), so "bursted" does not exist in standard English.
• D. burst: simple past. The bursting happened, and his confusion was an immediate reaction to it. This is the most natural and standard choice.

Why D fits best: "When his car tyre burst on the way, he did not know what to do" describes a sudden event followed immediately by a reaction. Both verbs are in the simple past, and that is exactly the pattern we want. The phrase "on the way" also tells us the bursting happened during the journey, as the trigger for his confusion rather than as background that came before.

Tip: Remember that "burst" has the same form in all three tenses: burst, burst, burst. Similar verbs are cost, cut, hit, hurt, put, set, shut. When "when" joins two quick, connected past events, use the simple past in both clauses. Also, never use "bursted" in an exam.