(a) They are getting used to (b) woke early, going to school, and (c) doing their homework. (d) No error.

• সাধারণত to এর পর Verb এর base form হলেও কিছু কিছু শব্দগুচ্ছ সমূহের পর verb+ing হয়।

• শব্দগুচ্ছ সমূহ হলো:
- With a view to,
- With an eye to,
- Accustomed to,
- Adhere to,
- Adverse to,
- Addicted to,
- Committed to,
- Confess to,
- Devoted to,
- Look forward to,
- Conducive to,
- Addicted to,
- Be used to,
- Get used to.

- উল্লিখিত বাক্যে Get used to এরপর wake (verb) এর Past form আছে।
- কিন্তু Get used to (verb) এরপর wake (live) + ing বসে।
- তাই, এখানে (b) ভুল।

• Correct Sentence: They are getting used to waking up early, going to school, and doing their homework.

Source: Advanced Learner's Communicative English Grammar & Composition By Chowdhury & Hossain.