Eating lots of vegetables and enough meat can keep you healthy all the time中keep为什么不能换成stay

keep和stay都可作半系词用,但stay后只接形容词,本句中构成固定短语,stayhealthy 保持健康；而keep除了可直接接形容词外,还可用于句型keep sb./ sth + adj 使……出于某种状态.因此,此句不可换.