下列程序执行后，得到的输出结果是
import re

p=re.compile(r'\bb\w*\b')

str="Boys may be able to get a better idea."

print(p.sub('**',str,1))

A.** may be able to get a better idea.
B.Boys may be able to get a ** idea.
C.Boys may ** able to get a better idea.
D.Boys may ** able to get a ** idea.