6. Jack — to train since… — to throw the ball 100 metres.

Длительное действие и достигнутый результат: has been training и has thrown.

Jack has been training since … — he has thrown the ball 100 metres.

Перевод: Джек тренируется с … — он бросил мяч на 100 метров.

Ответ: Jack has been training since … — he has thrown the ball 100 metres.