expert n. 专家;行家
adj. 熟练的;内行的;经验(或知识)丰富的
1. 此处是expert的形容词用法:
请看这个摘自柯林斯词典例句:
The Japanese are expert at lowering manufacturing costs. 日本人在降低生产成本方面很在行。
2. become 为系动词,后可以加形容词作表语。
类似例子:
I became interested in Chinese poetry when I was 7 years old. 我7岁时开始对中国诗歌感兴趣。