¿cuántos hermanos tienes? (3 points) question 6 options: 1) tengo tres hermanos. 2) voy al cine. 3) tienes tres hermanos. 4) tengo un vestido nuevo.

The correct answer is:  

1)  "Tengo tres hermanos."

Note:

The question/problem asks:  "¿Cuántos hermanos tienes?" ; 

→ which translates to:  "How many brothers do you have?" ; or, 
                                       "How many siblings do you have?" .

The only correct answer—and only answer choice that makes sense—is:

   1)  "Tengo tres hermanos."  (which translates into:  "I have three brothers." ;
                                                    or:  "I have three siblings." ;  
                                                          {among which at least one is a brother}.

Consider the other answer choices:

Choice 2)   "Voy al cine." ; which translates to:  " I am going to / I go to the movies/ movie theatre." ;  is completely illogical.

Choice 3)  "Tienes tres hermanos." ;  which translates to:

"YOU have three brothers." ;  or:  "YOU have three siblings."
                                                 {among which at least one is a brother} ;

is an illogical response to the question:  "¿Cuántos hermanos tienes?" ; 

                                                  {that is, "How many brothers do YOU have?" ; 
                                                         or;  "How many siblings do YOU have?"

Choice 4)  "Tengo un vestido nuevo." ; which translates to:
 
   " I have  a new dress." ;  is completely illogical.

That is correct! good job!