The underlined word "hone" in paragraph 4 most probably means ______.

A．It can greatly lengthen the tongue of South Koreans.
B．It is one display of craze for learning beautiful English.
C．Most families can afford it since it is such a simple operation.
D．Its current statistics are available, calculated at 10 procedures a month.

A．South Koreans do not care much about English pronunciation
B．their physical disability keeps them from doing so
C．Korean language does not include the phonetic sounds "L" and "R"
D．they are deaf to the different pronunciation of some letters