Which of the following sentences with introductory elements use correct punctuation? Check all that apply.
a)Since he had finished his presentation outline he started designing presentation visuals.
b)Introducing speakers before presentations, is always a challenge.
c)On my desk between the paperweight and the clock, you’ll find the form you need.
d)At the request of the governor’s office, the economic science lab produced various forecasting models.
e)Between sessions the conference participants visited the cafeteria.
f)When the account manager returns from lunch, we’ll double-check the meeting time.