1.他对这个国家的历史时间和人物十分了解.（historical)
He is well acquainted with historical dates and figures of this country.
He knows very well about this country's historical dates and figures.
2.警方已收到投诉函件,他们正着手进行调查.（complaint,look into)
The police has received the letter of complaint.And they are looking into it.
3.今天我们要集中讨论无家可归者的问题.（focus on)
Today we will focus on the problem of homeless people.
Today we’re going to focus on the question of homeless people.
4.电子邮件使全世界间的交流更加便捷.（E-mail,makc...faster and efficient)
The email has made the world's communication faster and efficient.
5.州政府声称已经减免了个人税.（claim,taxation)
The state government claimed that the individual income taxation has been reduced.
The state government claimed to have reduced individual income taxation.(个人税应该就是个人所得税哇?!)