mother's fault vs mother's blunder

[Arno]

English Synonym, Elementary Level

ESL/EFL Test #72 "Synonyms for mistake and error", question 10

The child broke the expensive vase but it was his mother's ......... for letting him play close to it.

(a) error
(b) defect
(c) fault
(d) blunder

English Synonym, Elementary Level

ESL/EFL Test #72 "Synonyms for mistake and error", answer 10

The child broke the expensive vase but it was his mother's fault for letting him play close to it.

Correct answer: (c) fault

Your answer was: correct
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how can we use blunder i mean when and in which context?

Arno

[Diverhank]

To me, blunder is a huge and stupid mistake or error and not a fault. Fault is the only proper choice in this case.