Correct Answer: Incontrovertible

Solution : The first option is the correct choice.

Incontrovertible means indisputable or unquestionable. Something that is incontrovertible cannot be denied or disputed due to its clarity or irrefutable evidence.

The meanings of the other options are as follows:

• Dubitable means subject to doubt or questionable.

• Frangible refers to something that is fragile or easily broken.

• Assailable means vulnerable or open to attack or criticism.

Therefore, the correct answer is, incontrovertible.