grateful 比较级和最高级为什么是more most

more beautiful; most beautiful
more delicious; most delicious
more ambiguous; most ambiguous
more interesting; most interesting
more important; most imprtant
more easily; most easily
more considerate; most considerate
more respectful; most respectful
more respectable; most respectable
more considerable; most considerable
more cheerful; most cheerful
more pleasant; most pleasant
more grateful; most grateful
more cautious; most cautious
more earnest; most earnest
more serious; most serious
more industrious; most industrious

这类词本身没有比较级和最高级，只能通过加more most 来表达出来

因为没有 gratefuler 这个东西。。