阅读理解。

     The Water World Swimming Pool is open every day from eight o’clock in the morning until half past

seven at night. It costs something to go to the pool. There is a special cheap price(价格)for students

with a student card. The price is one pound forty. But you must bring your student card with you.

      On Wednesday morning the pool is only open to mothers and babies. So mothers can enjoy a quiet

time in the water with their babies. Please leave your older children at home on Wednesday mornings.

      The new Water World Caf? is nearly finished. The caf? will open on the twenty-second in June. From the caf? you can watch the swimmers or enjoy a drink after you swim.

     Thank you for calling and we look forward to seeing you at Water world Swimming Pool.

     The Water world Swimming Pool

Opens: 8:00 a.m.

Closed: 1. _______

Cost for students: 2. _______

Wednesday mornings for mothers and 3._______

Caf? opens: 4_______

Leave older children at home:5_______

设一棵二叉树中，度为1的结点数为9，则该二叉树的叶结点的数目是______。

A．10

B．11

C．12

D．不确定