(____) What are those?

(____) Wow! You have a lot of animals! Are they sheep?

(____) Let me count. Mmm…Fifteen. Look, they are cows and hens.

(____) They're horses.

(____) Look! This is my farm.

(____) No, they aren't. They are goats.

(____) How many horses do you have?

(____) Your farm is so big. I like it.

已知直线$y=ex+1$与曲线$y=e^{x+a}$相切（$e$是自然对数的底数），则$a$的值是（   ）