I dont doubt

【答案】：B
在否定结构和疑问结构中，doubt为及物动词，如doubt后的从句完整无缺失信息，则选that为宾语从句的引导词。

扩展阅读：i dont give a shit ... i dont doubt the stock ... there is no doubt that ... dont push your luck ... it is obviously that ... we dont doubt he can ... i don t doubt whether ... i dont buy it ... it has been a long time ...