志愿者保持积极心态的策略有:()。
参考答案:自我激励、希望感、鼓励他人和宽容他人
国家标准GB13078—91规定,猪、鸡配合饲料中砷允许量不超过2mg/kg。
---What’s happening?
--- There was ____ accident just now.
A.a
B.an
C.the
D./