busy / lazy

  1. I’ve been (so) busy for a while.
    1a. I’ve been so busy the whole day.
    1b. I’ve been so busy for the whole day.

  2. She was a a lazy child who avoided household chores.
    2a. She was a a lazy child used to avoid household chores.
    2c. She is a a lazy child because she avoids household chores.
    Please correct those sentences.

There is a typo in set 2 which I shall ignore.

2a is incorrect. You need to include ‘who’ as in 2.

2c doesn’t make much logical sense. She is not lazy due to the fact that she avoids chores. It is more likely that she would avoid chores because she is lazy. For this reason, ‘and’ would work but ‘because’ doesn’t.