Fill in the correct form of verb.
He succeeded because he ______ hard (work).

Correct option is D

The correct option to fill in the blank is (d) worked.

Explanation:

The main verb succeeded is in the past tense, which shows the action already happened.

Therefore, the verb in the second clause must also be in the past tense to maintain consistency.

Correct sentence: He succeeded because he worked hard.

Grammatical Rule in English:

Rule of Tense Consistency:

When the main clause is in the past tense, the subordinate clause (reason clause with "because") is also generally in the past tense to maintain logical sequence.

Example:

·       She failed because she did not study.

·       They won because they played well.

Grammatical Rule in Hindi:

काल की संगति का नियम (Rule of Tense Consistency):

यदि मुख्य वाक्य (main clause) भूतकाल (Past tense) में है, तो कारण बताने वाला उपवाक्य (subordinate clause with “because”) भी प्रायः भूतकाल में होता है।

उदाहरण:

·       वह असफल हुआ क्योंकि उसने पढ़ाई नहीं की थी।

·       वे जीते क्योंकि उन्होंने अच्छा खेला।

Checking other options:

·       A. has been working → Present perfect continuous tense, doesn’t match past “succeeded.”

·       B. is working → Present continuous, tense mismatch.

·       C. works → Present simple, tense mismatch.