My bike was broken yesterday，so I____walk home．
句意:我的自行车昨天坏了，所以我不得不步行回家。
考查情态动词。might可能；had to必须，不得不；must必须，一定；could能，会，是can的过去式。must强调说话者的主观看法，have to强调客观需要。根据 “My bike was brokenyesterday我的自行车昨天坏了”可知，此处表达“所以我不得不步行回家”，用情态动词的过去式had to表示“不得不”。故选B。
My bike was broken yesterday，so I____walk home．
You________take me to the station. My brother’s taking me.
—According to the schoolrules, the students ________ get their ears pierced.
—I think that’s right.
—In China, many studentsfeel stressed because of too much homework.
—Don’t worry. Our government has realized this problem. I’m sure there________ be good news for them soon.
This book ________ be Jim’s.His name is on it.
—Look! There are so many people in the restaurant.
—Yes. The food there ________ be delicious.
—____________ we leave the library before 5 o'clock?
—No, you needn't. You can stay here until 5:30.
The biggest challenge weall face is to prevent further environmental disasters. We ________ take action before it is too late.
Listen up, guys!Everyone ________ wear a mask. Go and buy one if you don’t have one.
—Must I return this book before Friday, Sir?
—No, you ________,dear. You can keep it for two weeks.
