研制和开发不含碳并可工业生产的清洁能源,一直是科学家不懈追求的目标,目前液氨被人们视为一种潜在的清洁燃料。液氨燃烧的化学反应方程式为:4NH3+3O22N2+6H2O。和氢燃料相比有关数据见下表,据此判断正确的是② 以氨和氢为燃料时,可以减缓温室效应②氨泄漏到空气中比氢气更易发生爆炸③等质量的氨和氢分别燃烧,氢放出的热量少④氮的液化比氢容易得多
The children loved their day trip, and they enjoyed the horse ride ______.
Progress______ so far very good and we are sure that the work will be finished on time.
Charles was alone at home, with_______ looking after him.
It is often ______ that human beings are naturally equipped to speak.
I can’t leave. She told me that I ______ stay here until she comes back.