Tenses

Tenses	Simple	Continues	Perfect
Present	I am sit on the chair     S+V1	I am siting on the chair     S+Be+Ving	I have sat on the chair already S+Have (Has)+V3
Past	I sat on the chair   S+V2	I was siting on the chair   S+Was/Were+Ving	I had sat on the chair   S+Had+V3
Perfect	I shall sit on the chair   S+Shall/Will+V1	I shall siting on the chair   S+Shall/Will be+Ving	I shall sat on the chair   S+Shall/Will have+V3