Bài giải:

P(x) = $3{{x}^{2}}+2{{x}^{3}}+2x+5-{{x}^{2}}-x$   

= $2{{x}^{3}}+(3{{x}^{2}}-{{x}^{2}})+(2x-x)+5$

= $2{{x}^{3}}+2{{x}^{2}}+x+5$

Q(x) = ${{x}^{3}}-2x-2+3x-{{x}^{2}}+1$

= ${{x}^{3}}-{{x}^{2}}+(-2x+3x)+(-2+1)$

= ${{x}^{3}}-{{x}^{2}}+x-1$

P(x) + Q(x) =  $2{{x}^{3}}+2{{x}^{2}}+x+5$ +  ${{x}^{3}}-{{x}^{2}}+x-1$

= $(2{{x}^{3}}+{{x}^{3}})+(2{{x}^{2}}-{{x}^{2}})+(x+x)+(5-1)$

= $3{{x}^{3}}+{{x}^{2}}+2x+4$

Vậy đáp án đúng là: A