What happens to the Master-Detail relationship with Contacts?

Universal Containers has a junction object called Invoices with a primary Master-Detail relationship with Accounts and a secondary Master-Detail relationship with Contacts. The app builder has a requirement to change the primary Master-Detail relationship to Lookup.

What happens to the Master-Detail relationship with Contacts?
A . The Contacts Master-Detail values are cleared from invoices.
B . The Contacts Master-Detail also converts to Lookup.
C . The Contacts Master-Detail field is deleted from the object.
D . The Contacts Master-Detail becomes the primary.

Answer: D

Explanation:

Explanation – The second master-detail relationship you create on your junction object becomes the secondary relationship. If you delete the primary master-detail relationship or convert it to a lookup relationship, the secondary master object becomes primary. https://help.salesforce.com/HTViewHelpDoc?id=relationships_considerations.htm&languag e=en_US