9) Jill has (put on/lost) weight. She has become obese.

Решение:

Фраза 'She has become obese' (Она стала толстой) прямо указывает на увеличение веса. Поэтому наиболее подходящим вариантом будет 'put on weight' (набрать вес).

9) Jill has put on weight. She has become obese.

Ответ: put on