Решение:
I am writing a letter to my grandmother.
Отрицание: I am not writing a letter to my grandmother.
Вопрос: Are you writing a letter to your grandmother?The birds are flying in the sky.
Отрицание: The birds are not flying in the sky.
Вопрос: Are the birds flying in the sky?My sister is drawing a picture now.
Отрицание: My sister is not drawing a picture now.
Вопрос: Is your sister drawing a picture now?They are fixing the bike.
Отрицание: They are not fixing the bike.
Вопрос: Are they fixing the bike?The kids are watching television now.
Отрицание: The kids are not watching television now.
Вопрос: Are the kids watching television now?You are running in the park with the day.
Отрицание: You are not running in the park with the day.
Вопрос: Are you running in the park with the day?
Надеюсь, данное объяснение поможет вам понять, как вставить пропущенные буквы и составить отрицание и вопрос в данных предложениях.