一道英语完型,The experience does not have to be formally organised

一道英语完型,
The experience does not have to be formally organised."We're not just interested in easily identifiable skills," says Goodman." for instance,one student took the lead in dealing with a difficult landlord and so __79__ negotiation skills.We try to make the experience relevant to individual lives."
A) demonstrated B) determined C) operated D) involved