15. We ________ (plan) to buy you a cake for your birthday at this time yesterday, but the bakery was closed.
Для решения этого задания необходимо определить, в каком времени нужно употребить глагол в скобках: Past Simple или Past Continuous.
Глагол (plan) описывает действие, которое длилось в определенный момент в прошлом, поэтому используем Past Continuous. Форма глагола plan в Past Continuous - were planning.
Таким образом, предложение будет выглядеть так:
We were planning to buy you a cake for your birthday at this time yesterday, but the bakery was closed.
Ответ: We were planning to buy you a cake for your birthday at this time yesterday, but the bakery was closed.