1 If you...had looked... (look) both ways before crossing the street, you wouldn't have been knocked down.

Решение:

1. If you had looked (look) both ways before crossing the street, you wouldn't have been knocked down.

Объяснение:

Здесь используется третье условие (Third Conditional). Первая часть предложения (if-clause) должна быть в Past Perfect. Форма 'had looked' является правильной.