present 既可以当形容词,也可以当动词
The experts present at the meeting(出席会议的)were from different parts of the world.
在此句子中,that be被省略了.即为The experts （that were） present at the meeting(出席会议的)were from different parts of the world.that 后的从句（were present at the meeting）都是修饰experts的.而此从句是主语从句,即that＝experts.若单省略that,一句中就有两个动词,就有语法错误了,所以省略时把that be一起省略了.