Essential-Unit 3-Major subways

v. , to compete with

n. , a person travellng on foot

v. , to appear

v. , to fill so much as to make movement difficult

n. , the main or most important feature

adj. , stopping the usual course of activit

n. , the outer part or top of something

v. , to let something out

adv. , below the ground

n. , the working of something, being used