Fill in the gaps with the correct word.

1. A: What would you like for breakfast?
B: A ... of cereal, please.
2. A: How many raisins do we need for the cake?
B: Just a ... .
3. A: How about a ... of lemon in your drink?
B: Oh yes, please.
4. A: It's my birthday today. Please have a ... of cake.
B: Thanks a lot!