Explanation
Correct answer: D.
Choice D is the best answer. The subject of the modifier “a nearly frictionless state” is “superlubricity.” Subject-modifier placement requires a modifier and its subject to be next to one another, so “superlubricity” must be the first word in the missing clause.
Why the other choices are wrong
Choice A
Choice A is incorrect. This choice creates a subject-modifier placement error. The subject of the modifier “a nearly frictionless state” is “superlubricity.” Subject-modifier placement requires a modifier and its subject to be next to one another, so “superlubricity” must be the first word in the missing clause.
Choice B
Choice B is incorrect. This choice creates a subject-modifier placement error. The subject of the modifier “a nearly frictionless state” is “superlubricity.” Subject-modifier placement requires a modifier and its subject to be next to one another, so “superlubricity” must be the first word in the missing clause.
Choice C
Choice C is incorrect. This choice creates a subject-modifier placement error. The subject of the modifier “a nearly frictionless state” is “superlubricity.” Subject-modifier placement requires a modifier and its subject to be next to one another, so “superlubricity” must be the first word in the missing clause.