​Language is considered a significant (31) of communication in international relations

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase for each of the blanks.

Language is considered a significant (31)............... of communication in international relations. People in modern world have no longer been bound to their own countries. Moreover, in keeping (32)........ with speedy scientific developments nowadays, they must widen their (33)............... relations with those highly developed nations in other parts of the world, owning to the fact that no one is able to (34)............... with any natives in the world, it is necessary for people to choose to learn a foreign language as a word-wide common means of communication (35)...... their own mother tongue or native language. That is why English has been chosen by most people to be a foreign language to master. More and more people use English and the number of those who lean English as a foreign language has been increasing so rapidly that it has outnumbered that of any other.