hazeleyedgirl“
What do the following words have in common?
What has happened to them in Modern English?
wilt, hast, thine, art
”
You all fail! Any fool can tell that the words are old. Of course they are old in an exam based on Old English! 
What do the following words have in common? - They are all grammatically restricted to the second person singular; in modern English: you will, you have, yours, [you] are.
What has happened to them in Modern English?
There was no future tense in Old English even though the predecessor of will was sometimes used to indicate future action. Its meaning was "to want, to desire" and will has mostly lost this meaning. It is still present in some contexts, for example when will is used with if: You may come if you will (= if you want to).
So, the meaning of wilt/will has changed and the inflected form is no longer used.
As there was no perfect tense in Old English, hast/have has acquired a new use. In addition to the Old English use, which remains in Modern English, it is now used as a present perfect auxiliary. The perfect tense was developing in Old English and sentences corresponding to modern I have written it were sometimes uttered but the speaker understood the have as a present tense verb and the past perfect written indicated the state in which "it" was. In other words, written was adjectival in character.
Have has acquired lots of new uses since the early days, for example "to have something done": I had my hair cut yesterday.
Thine is related to thou and thee, and all three may occur in archaic texts end religious contexts even today. I think most Americans know the songs A Closer Walk With Thee and How Great Thou Art.
CB