必要时的英文：at a pushIf it comes to the pinchin necessityon occasion参考例句：If appropriate, the environmental conditions shall be controlled and/or monitored.必要时,环境条件应予以控制或监控。If necessary, nylon, acrylic and polyester fibers may be bleached with sodium chlorite under acidic conditions.在必要时,尼龙、丙烯腈、涤纶纤维可在酸性条件下用氯化钠漂白。They were ready to die, if necessary, for their country.
小小亦儿
