Note that $$4.07-4 = 0.07$$; $$4-3.925 = 0.075$$; $$4-3.979 =0.021$$; $$4.12-4 = 0.12$$ and $$4.024-4 = 0.024$$.  So, of the five options, $$3.979$$ is nearest to $$4$$. 
Which of these is closest to $$4$$? 

[a] $$4.07 $$ 
[b] $$ 3.925 $$ 
[c] $$3.979 $$ 
[d] $$4.12 $$ 
[e] $$4.024$$ 