观测工作借助于各种望远镜。The observational work is carried out on a range of telescopes.天文学家们正在观测木星.The astronomers were taking an observation of Jupiter.许多机关通过直接的观测收集信息.Many agencies gather information through direct observation....
Some acids are strong enough to burn the wood.有些酸的酸性强得可以烧坏木头.There are many amino acids that the body cannot synthesise itself.有许多种氨基酸人体自身不能合成.How do acids react on metals?酸对金属会起什么样的化学反应?...