What is the difference between 'affect' and 'effect'?

[Oksana]

English Language Tests, Intermediate level

ESL/EFL Test #218 "Confusing Words test (1)", question 1

How much of an ......... did World War II have on Europe?

(a) affect
(b) effect
(c) effects
(d) affects

English Language Tests, Intermediate level

ESL/EFL Test #218 "Confusing Words test (1)", answer 1

How much of an effect did World War II have on Europe?

Correct answer: (b) effect

Your answer was: incorrect
How much of an affect did World War II have on Europe?
_________________________

What is the difference between 'affect' and 'effect'?

Thanks

[Mister Micawber]

.
AFFECT vs EFFECT.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber