Combine the following sentences into one simple sentence.
He was very dull. He could not understand.

Correct option is D

The correct answer is (d) He was too dull to understand.
Explanation:
To convert two sentences into a simple sentence, we use the "too...to" construction.
· "Too" indicates an excessive degree.
· "To understand" is an infinitive phrase acting as the result of being too dull.
Corrected Sentence: He was too dull to understand.
Grammatical Rule Used:
· "Too + adjective + to + verb" is used to express impossibility or inability due to excessiveness.
Meanings of other given options:
· (a) He was so dull and could not understand. → Incorrect because "so dull" needs "that" to complete the meaning. · (b) He was very dull that he could not understand. → Incorrect because "very dull that" is grammatically incorrect; "so dull that" would be correct. · (c) He was too dull that he could not understand. → Incorrect because "too" should be followed by "to," not "that."