3.
a) We use was and were to talk about a situation in the past.
b) In "When was Instagram founded?" was refers to Instagram, that is, third person singular.
c) In "Were Mike Krieger and Kevin Systrom students at the same university?" were refers to Mike and Kevin, that is, third person plural.
d) When we ask questions, the verb to be comes before the subject.
4.
a) Kelly was studying yesterday.
b) I was talking about games with Eliot.
c) What was happening to you yesterday?
d) I think the car was making noise because it's old.
e) The door and the window were blocking the wind.
5.
nessa aqui, eu vou só traduzir as perguntas pq as respostas são pessoais tá? mas se precisar de ajuda pode chamar
a) O que você estava fazendo ontem às 20h?
b) A última vez que você usou seu celular, o que você estava vendo?
c) O que você estava comendo em sua última refeição?
d) Você se lembra da última coisa que você bebeu? O que você estava bebendo?
e) Com o que você estava sonhando quando acordou hoje?
