Questions 139~142 refer to the following news release.

Birmingham, UK - A leadership conference held in Birmingham brought together __139__ experts in the field to discuss the development of leadership skills. Attendees were able to gain __140__ and ask questions from the diverse group of professionals from various industries.
 "I learned so much about what __141__ to be a successful leader and how to develop the skills needed to excel in my career." said an attendee.
The conference was a great success, with attendees leaving with a newfound sense of confidence. The event organizers are already planning next year's conference and are excited to continue providing __142__ learning opportunities for professionals in the Birmingham area. 
 Contact:Bernie SmithOrganizer, Birmingham Strong Leadership [email protected]
【題組】139.
(A)a panel of
(B)a considerable amount of
(C)a plenty of
(D) a series of