________you smell something burning? Go and see what's happening.
下面四个交通标志图是轴对称图形的是（ ）
—Could you hang out with me, Kate?
—Sorry, I ________. I have to do my homework.
“天问一号”在经历了7个月的“奔火”之旅和3个月的“环火”探测，完成了长达5亿千米的行程，登陆器“祝融”号火星车于2021年5月15日7时18分从火星发来“短信”，标志着我国首次火星登陆任务圆满成功，请将5亿这个数用科学记数法表示为（ ）
We ________ see which way to go if the stars do not twinkle（闪耀）so.
下列数轴表示正确的是（ ）
Bill is running so fast!I _________ believe my eyes.
|-2021|=
— Good news? You’ve passed the PE test.
— Hooray! ______,I was worried about it.
