11. A bush has 10 branches. Each branch has either 5 leaves only or 2 leaves and 1 flower. Which of the following could be the total number of leaves the bush has?
A 45
В 39
C 37
D 31
E None of A to D
11. E The maximum number of leaves the bush could have is $10 \times 5=50$. Each branch that has two leaves and a flower instead of five leaves reduces the number of leaves the bush has by three. Therefore the total number of leaves the bush has is of the form $50-3 n$ where $n$ is the number of branches with two leaves and a flower. It is straightforward to check that none of options A to D has that form and so the answer is $\mathrm{E}$.