Explanation
Correct answer: D.
Choice D is the best answer. The convention being tested is pronoun-antecedent agreement. The singular pronoun "he" agrees in number with the singular antecedent "Félix González-Torres," and it clearly indicates that González-Torres created the additional installations.
Why the other choices are wrong
Choice A
Choice A is incorrect because the plural noun phrase "they all" doesn’t agree in number with the singular antecedent "Félix González-Torres," and it doesn’t clearly indicate that he (González-Torres) created the additional installations.
Choice B
Choice B is incorrect because the plural pronoun "those" doesn’t agree in number with the singular antecedent "Félix González-Torres," and it doesn’t clearly indicate that he (González-Torres) created the additional installations.
Choice C
Choice C is incorrect because the plural pronoun "both" doesn’t agree in number with the singular antecedent "Félix González-Torres," and it doesn’t clearly indicate that he (González-Torres) created the additional installations.