大家好，我想詢問的句子如下↓↓
What was once nearly dismissed as a stale brand has been reinvigorated.
這裡句首的what，是否有運用到什麼文法呢？
句子的主要動詞是 has been嗎？
謝謝

What = the thing that 複合關代，主要動詞 has