A burro is carrying salt of one large bag backcross a river.有一头驴子驮着一大袋子盐过河.The method can be conveniently applied to practical backcross breeding programs.该方法可以很方便地应用于实际的回交育种....
“求求你留下来给我读点东西吧，妈妈，”他央求道。"Please stay and read to me, mummy," he beseeched.她用的是央求的语气。Her voice was pleading.我再三央求, 他才答应帮忙.He made a promise of help, as I pleaded with him again and again....