问题
选择题
During the dialogue with Chinese youth in Shanghai, President Obama announced the U.S. would expand the number of students to study in China to 100,000 _______ ties between the two countries.
A．strengthening
B．strengthened
C．to strengthen
D．to be strengthened
答案
答案：C
表示做某事的目的用动词不定式to do，strengthen为加强的意思，故本题选C。