答案：A

解析：

The word “but” along with the word “concessions,” which refers to yielding to something, suggests that there is some contrast in the first part of the sentence. An architect certainly might want to “maintain” his initial vision and design, but as a result of needing to accommodate, or consider and allow for, requests from the client, he might have to change them. It makes sense to suggest that the architect made concessions and accommodated the client’s requests even though he wanted to keep his initial vision and design unchanged.