Pentavalency
五价
🗣️ 情景例句
About forty minutes, I think.
我想大约40分钟。
He emerged as leader at the age of thirty.
他在30岁时出人头地成为领袖。
There's a talk on cancer that might be quite interesting, so perhaps I'll go to that.
有个关于癌症的报告可能很有意思，也许我会听听。