What is the difference between slay and slew?

[Slasherstorm]

English Language Tests, Intermediate level

ESL/EFL Test #263 "Irregular Verbs Test (11)", question 7

The hero in the children's story ......... the horrible dragon.

(a) slay
(b) slew
(c) slaying

English Language Tests, Intermediate level

ESL/EFL Test #263 "Irregular Verbs Test (11)", answer 7

The hero in the children's story slew the horrible dragon.

Correct answer: (b) slew

Your answer was: incorrect
The hero in the children's story slay the horrible dragon.
_________________________

why answer not slay?

Slasherstorm

[Conchita]

In the test sentence, the verb tense used is the simple past. The story could also be told in the present tense, but it would have to be 'slays'.