【2015•湖南】When the clerk saw a kind face wrinkled in an apologetic smile, she stood rooted to the ground, ________ whether to stay or leave.
54. The football fans cheered their team _____ the entrance _____ the field.
53. Our music teacher often enjoyed _____ playing the violin in his spare time.
52. The struggle against sand storm will not end _____ victory unless we pay much attention to the balance of nature.
51. Don’t put your cell (手机) _____ the edge of the table, or it will fall off
50. The Englishman has a very good ear _____ music. You can ask him for some advice.