The man holding two cans of soda over there __ eat five burgers in 10 minutes. a. are able to c. were able to b. is able to d. has been 2. This group of doctors __ in important research. a. is involved c. are involved b. be involving d. been involving 3. Mathematics __ not easy for my brother. a. was c.are b. were d. be 4. The results of our efforts to get more business __ been successful. a. have c. having b. has d. was 5. The computers ordered last week __ on solar power. a. run c. runs b. running d. to run Nurhida.amin 7. The United States __ taxes to develop the infrastructure for commerce. a. raise c. raises b. rise d. risen

1. **b. is able to**The subject is "man" (singular), so the verb must agree. "Is able to" is the correct singular present tense form. The sentence describes a current ability.2. **a. is involved**The subject "group" is singular, even though it refers to multiple doctors. Therefore, the singular verb "is" is correct.3. **a. was**The subject is "Mathematics," which is treated as a singular noun. The sentence describes a past state, so the past tense "was" is appropriate.4. **a. have**The subject is "results," which is plural. The sentence describes a completed action with a continuing effect, so the present perfect tense "have been" is correct.5. **a. run**The sentence describes a characteristic of the computers. The simple present tense "run" indicates a habitual or general truth.7. **c. raises**The subject is "The United States," which is singular. The sentence describes a habitual action, so the singular present tense "raises" is correct.