Resposta:

a) Karen has sent me an e-mail. (to send)

b) Dave and Pat have visited the museum. (to visit)

c)I have been at the pet shop. (to be)

d) They have packed their rucksacks. (to pack)

e) Marcus has had an accident. (to have)

f) We have done the shopping for our grandmother. (to do)

g) I have just cleaned my bike. (to clean)

h) Emily has painted her room. (to paint)

i) Lisa and Colin have gone to a concert. (to go)

j) My friends have given up smoking. (to give up)

Explicação:

Para formar uma frase no Present Perfect você precisa de duas coisas:

1 - Utilizar o verb auxiliar "have".

2 - Colocar o verbo principal no Past Participle. Para descobrir qual é a forma de um verbo no Past Participle, você pode consultar a lista que está em anexo.

Cuidados: Quando o sujeito da frase for He/She/It, você deve utilizar o verbo "have" na terceira pessoa, que é "has".