Answer: Last option.
Step-by-step explanation:
By definition, the square of a binomial is:
[tex](a+b)^2=a^2+2ab+b^2\\\\(a-b)^2=a^2-2ab+b^2[/tex]
Keeping the above on mind, you have the following expression given in the problem:
[tex](x+5)^2[/tex]
Therefore, if:
[tex]a=x\\b=5[/tex]
You obtain the following trinomial:
[tex](x+5)^2=x^2+2(x)(5)+5^2=x^2+10x+25[/tex]
Therefore, the answer is the last option.