Select the most appropriate option to substitute the highlighted segment in the given sentence.
Regard of whether the students were ready or not the teacher announced the dates of the test.

Correct option is D

The correct substitution of the highlighted words is (d) Regardless of whether.
Explanation: The phrase "Regardless of whether" is the correct conjunction to indicate that the teacher made the decision without being influenced by whether the students were ready or not.
Grammatical rule used: “Regardless of” is a subordinating conjunction that means “without being affected by something.”
Example: Regardless of the rain, we will continue the match.
Information Booster: “Regard of” is incorrect; “regarding” is a preposition, not a suitable replacement for this construction.