<單字複習>
已選單詞
area
asset
barrier
boundary
challenge
code
communication
compound
danger
data
difficulty
domain
edge
element
estate
fact
field
information
intelligence
issue
knowledge
land
limit
margin
material
matter
message
mixture
obstacle
password
privacy
problem
property
region
resource
risk
room
safety
security
signal
solution
space
substance
territory
threat
wisdom
zone
