What is the simple subject of the following sentence "a virus is a microscopic organism."

Virus is the simple subject because the subject is whatever is before the verb
and in this case'is" is the verb

Dr.king , i would take my mental flight by egypt and i would watch god’s children in their magnificent trek from the dark dungeons of egypt through, or rather across the red sea, through the wilderness on toward the promised land.his  speech"i  have a dream" to encourage people that change will come. this  speech  was very important during the civil rights movement and was a contributing factor in the end of racial injustice in society. the  intended audience  of "i  have a dream" is white people. i hope this