[单项选择题] MOTO参数中已知：max_number_of_sdcch=24、number_sdcch_preferred=16sdcch_need_high_water_mark=4、sdcch

[单项选择题] MOTO参数中已知：max_number_of_sdcch=24、number_sdcch_preferred=16sdcch_need_high_water_mark=4、sdcch_need_low_water_mark=16，当sdcch被占用几个时，TCH会向sdcch转换（）

A.24

B.21

C.12

D.13