请根据短文的内容，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词，并注意使用该词的正确形式。

It has been two years since I began to study abroad on my student exchange program in America. I think it was really a valuable e for me.

At first, I was a s and quiet girl. The teacher spoke so fast that I couldn't u her most of the time . My spoken English was also weak. Because of my poor pronunciation(发音), I was afraid to speak English in class.

Thanks to my classmate — Carl, he advised me to join a study group. They encouraged me to be brave and confident. I practised speaking English with them over and over again. I d a few good English learning habits such as asking questions bravely. I made progress in learning English. For example, now I can pronounce the words c.