Поставьте глаголы в скобках в present perfect или past simple. 1) these tasks … (have) many difficulties. 2) … production managers … (analyse) these data yesterday? 3) a constructor … (build) a house. 4) they … (investigate) the problem a week ago. 5) inflation … (affect) on the economy a lot. 6) early settlers … (preserve) meat by drying and salting it. 7) they … (just/elect) the president of the company. 8) the children … (skate) on the frozen pond last winter. 9) the department … (already/mail) out 200 notices. 10) when he … (return) home they … (not/be) ready. 11) the olympic committee … (announce) the results. 12) we …(be) here since ten o'clock.