① ____ A. subject B. us C. music
② ____ A. six B. like C. swim
用纯种的黄色圆粒豌豆与绿色皱粒豌豆杂交,F1全部是黄色圆粒,F1自交的F2,在F2中杂合的绿色圆粒有1000个,推测纯合的黄色皱粒有( )