The pencil is one of the most common writing tools in the world. In fact, pencils are made in the billions each year.Pencils create marks that can be easily (1) ........................ but are not affected by temperature, water or chemicals. As a result, pencils can be used by divers underwater, or (2) ...................... in space. Most pencils are round and hexagonal so they are comfortable for users to (3) ........... while writing. The key material for the pencil core is called graphite, a form of carbon that was discovered in large quantity in Cumbria, England back in 1565. People back then thought this material was a form of lead, so in many (4) ....................., the word that describes this type of pen literally means lead pen. A.erased B.extracted C.cleaned D.deleted A.explorers B.pilots C.adventurers D. astronauts A.keep B.save C.hold D.embrace A.languages B.cultures C.customs D.people Giúp mình với ạ . Cảm ơn nhìu