Какие сложные эфиры могут иметь один и тот же состав C4H8O2 ? Напишите формулу изомеров и дайте их названия. заранее спасибо

Раскройте скобки,употребляя глаголы в одном из следующих времён:Present,Past,Future,Simple;Present,Past Continuous.

1.Look at the children:they (to skate) very well.

2.You (to skate) last Sunday?-Yes, we (to skate) the whole day last Sunday.We (to skate) again next Sunday.

3.My brother can skate very well.He (to skate) every Sunday.

4.What you (to do) now?-I (to wash) the dishes.

5.What you (to do) at three o'clock yestarday?-I (to have) dinner.

6.You (to have) dinner now?

7.Where your brother (to work)?-He (to work) at an institute.

8.Your grandmother (to sleep) when you (to come) home yestarday?

9.What your brother (to do) tomorrow?

10.I (not to go) to the shop yestarday.I (to go) to the shop tomorrow.

11.Where Kate (to go) whhen you (to meet) her yestarday?

12.Every day the boss (to enter) the office at nine o'clock.

допоможіть! поясніть явище алотропії на прикладі Оксигену та Сульфуру. Визначте значення озонового шару для життя організмів на Землі.

найдите три решения уравнения y-5=0, x+3=0