OG详解-OG3 文法 Q1

Choice A is the best answer. The convention being tested is the use of finite and nonfinite verb forms within a sentence. Relative clauses, such as the one beginning with “which,” require a finite verb, a verb that can function as the main 
verb of a clause. This choice correctly supplies the clause with the finite past tense verb “provided.” 
Choice B is incorrect because the nonfinite participle “having provided” doesn’t supply the clause with a finite verb. Choice C is incorrect because the nonfinite to-infinitive “to provide” doesn’t supply the clause with a finite verb. Choice D is incorrect because the nonfinite participle “providing” doesn’t supply the clause with a finite verb.