Skip to content
Prep
Freely
Home
TOEFL
IELTS
Guides
Log in
Sign up
P
Account
Profile
My progress
Settings
Log out
TOEFL
/
Listening practice
/ Section PVNL
Listen to an Academic Talk
Listen to a talk in an engineering class.
Listen
42. What did researchers previously believe about the white lumps in Roman concrete?
A
They were added to make the concrete lighter.
B
They were the result of poor mixing.
C
They came from seawater.
D
They made the concrete crack.