Indicate the word or phrase closest in meaning to the underlined word(s) in each of the following questions
Biogas can be utilized for electricity production, cooking, space heating, water heating and process heating.
Mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the following questions.
A cooperative program between China and Germany on building Yangzhow, a famous ancient city, into a(n) ________ city has proceeded smoothly since it started in September last year.