Do/does - did в прошедшем
didn't, соответственно
<span>1. Today scientists are still looking (pres cont active) for the substance as a source of energy.
2. Could (past simp act) you speak English a year ago?
3. The Mendeleyev system has served (pres perf act) for almost 100 years as a key to discovering new elements.</span><span>
1. Сегодня ученые все еще ищут вещество - источник энергии.
2. Могли вы говорить по-английски год назад?
<span>3. Система Менделеева уже почти 100 лет служит ключом к открытию новых элементов.</span></span>
The cats aren't slepping jn the house
1. Who does take patients in the emergency department?
2. What patients can get a referral from the doctor clinic?
3. What is the nurse on duty doing?