Answer:
B
Explanation:
There is no need for tenses if the date/ time has been established.
It's we are calling or we used to call
我不完全了解原因,因为我是初学者,但似乎还可以
Wǒ bù wánquán liǎojiě yuányīn, yīnwèi wǒ shì chū xuézhě, dàn sìhū hái kěyǐ
对不起,浪费我的时间,我不明白
Duìbùqǐ, làngfèi wǒ de shíjiān, wǒ bù míngbái
i basically said sorry and you can translate the rest