Answer:
1= tallest, 2= heaviest,3= hardest 4=busiest
The tundra is a harsh envioroment so only the toughest plants and animals can survive.
The sentence whose style is most appropriate with respect to clarity and simplicity of language is the first one - For centuries, art admirers have been digging through records of the painting to figure out its meaning.
The other sentences use language that is quite complicated.
