a)When you phoned, I was thinking about you.(to think)

b)The child was playing while her mother was preparing the dinner.(to play - to prepare)

c)She was walking in the Forest and the wolf was watching.(to Walker - to match)

d)Were you working hard last night?(to work)

e)The girls New clothes yesterday.(to dress - negativa)  ?

f)We were watching a film about Chinese culture in our last classe.(to watch - negativa) ?

Explicação:

Os pontos de interrogação em negrito significam que não deu pra entender qual o requisito nas frases.