It was made of soft lumber, spruce by the look of it.其制作材料是软木，看起来像是云杉。Lumber casts.木料会变形扭曲。Forested areas have been expanding every year, with the increase in standing timber greater than that of felled lumber.森林面积每年都在增加...
This apparatus produces harmful radiations.这种仪器会产生有害的辐射物.Most metallic and some nonmetallic elements will emit characteristic radiations.大多数金属和某些非金属元素都会发出特征的射线.Our knowledge regarding the effects of ionizing radiations i...