单选题 A spokesperson for Solaris International announced that the company would ______ on strengthening investor relations in South America.
A. repeat B. surpass
C. franchise D. concentrate

【正确答案】 D
【答案解析】[解析] concentrate on表示“专心于……”，符合题意，表示“公司将致力于牢固投资者的关系”。其他三项后面都不能跟介词on连用。故本题正确答案为D。