Какое время? tom and bill went to london last year.

tom   and bill went to london last year. - том и билл ездили в лондон в прошлом году.

 

past simple - потому что глагол went во второй форме от инфинитива to go и временной показатель last year - в прошлом году

past simple, т.к. "last year" и глагол во 2 форме.

41. is concrete a natural or artificial stone? 2. what kind of properties it has? 3. in what way can concrete be used in moulds? 4. does it resist fire? 5. is concrete used in skeleton structures? 6. how many functions have aggregates? 5. 1. in other words aggregates can be defined as a mass of practically inert mineral materials, which 2. all aggregates both natural and artificial which have sufficient strength and resistance to watering and which do not contain harmful impurities may be used for making concrete. 3. as aggregates such materials as sand, pebbles, broken stone, broken brick, gravel,slag, sinder, pumice and others can be used. 4. it sets under water, can be poured into moulds so as to get any desirable form. 6. 1. can 2. may 3. must 4. can 5. has to help 7. sets,can be poured, has, resists.- present simple.