Keep a pad handy to jot down queries as they occur.手边放一本便笺簿，以便有问题时随时记下。To make it easier to contact us, keep this card handy.把这张卡放在手边，以便于和我们联系。That key will come in handy if you lock yourself out.要是你把自己锁在了屋外，那把钥匙就派上用场了。...
这四枚新邮票是为了纪念英国天文协会成立100周年而发行的。The four new stamps mark the 100th anniversary of the British Astronomical Association.在历史的年代数目和天文年代数目之间存在差别.There are differences between historical and astronomical numbering of years.数学材料是...