OG详解-OG7 文法 Q30

Choice C is the best answer. The sentence indicates the year Yosemite Falls was completed, stating that it was completed in 1930. 
Choice A is incorrect. The sentence indicates where Obata created black ink paintings; it doesn’t indicate when the painting was completed. Choice B is incorrect. While the sentence identifies Obata as an artist who created a notable painting, it doesn’t indicate when that painting was completed. Choice D is incorrect. The sentence identifies the method Obata used; it doesn’t indicate when the painting was completed.