mostly為什麼可以加be動詞

mostly是個副詞，副詞可修飾形容詞，而形容詞可以放在be動詞後面，即be mostly+形容詞，例如：

1、The hard-line speech appears to be mostly for domestic consumption強硬路線的講話似乎主要是説給國內人聽的。

2、Indeed， our schools and universities are structured to mould pupils to be mostly obedient servants of rationality， and to develop outdated skills in interacting with outdated machines.實際上，學校和大學就是用來把學生塑造成理性的服從者，培養與過時機器互動的過時技能。

3、And my talk today will be mostly about these cognitive traps.我今天將主要談論這些認知陷阱。