Select the most appropriate option to fill in the blank.
She decided ______ the challenging task of learning a new language during her summer break.

Correct option is D

The correct option to fill in the blank is (d) to undertake.
Explanation: After certain verbs like "decide", the infinitive form of a verb (to + base verb) is used.
• "She decided to undertake" follows the standard verb + infinitive pattern.
Example: She decided to join the yoga class in the evening.
Explain why other options are incorrect:
· (a) undertake: Base verb; grammatically incorrect after "decided".
· (b) undertook: Past tense form; does not follow "decided" correctly.
· (c) to undertaking: Incorrect infinitive construction. "To" is not followed by a gerund.