B4

Graffiti is any type of public markings that may appear in the forms of simple written words to elaborate wall paintings. Graffiti has existed since ancient times.
(present perfect, т.к. существовала и существует до сих пор)

EXIST

B5

The earliest forms of graffiti date back to 30, 000 BC in the form of prehistoric cave paintings and pictographs using tools such as animal bones and pigments.
(степень сравнения)

EARLY

B6

The images drown on the walls showed scenes of animal wildlife and hunting expeditions. These illustrations were placed in ceremonial and sacred locations inside of the caves.
(past simple passive, т.к. это было в определённый момент в прошлом.
Их поместили)

PLACE

B7

Modern graffiti comes in many different forms, from the scrawled message in a public bathroom stall to the spray-painted murals boasted on subway walls.
(present simple, т.к. это общее утверждение)

COME

B8

Nowadays, paint, particularly spray paint, and marker pens have become them most commonly used graffiti materials. 
(степень сравнения)

COMMONLY

B9

In most countries, marking or painting property without the property owner’s consent is considered to be vandalism, which is a punishable crime.
(указание принадлежности предмета)

OWNER

B10

Because of the controversial material contained in many murals, graffiti is now considered to be a form of resistance art, in rebellion against common public beliefs and government laws.
(верований)

BELIEF