英语翻译
IM interaction are infused with a level of serendipity and the possibility of chance encounters online that are unique to the medium.Some applications allow users to set a status of "hidden." Even though you can not tell they are online,they might suddenly send you a message.You can send a message to someone who is logged in,but perhaps she is away from her computer.Maybe she is in class or otherwise occupied but hasn't set her status to show that.
PS:不要用翻译软件,注意语法顺序,尽快,