Answer:
El carro negro no está detrás del carro blanco. Está ADELANTE del carro blanco. 
Step-by-step explanation:
To better understand why ADELANTE is the correct option we first need to remember what the function of the ADVERBS within a sentence is.
WHAT IS AN ADVERB? 
It is a kind of word that qualifies a verb an adjective or even another adverb. 
 In Spanish we have different types of adverbs that point to various themes about the verb:
 1. ADVERBS OF PLACE: They indicate where the action of the verb occurred. 
 2. ADVERBS OF MOOD: They indicate how the speaker evaluates the situation.
 3. ADVERBS OF TIME: They indicate when the action of the verb occurred. 
 4. ADVERBS OF QUANTITY: They indicate the quantities about what happened.
In our exercise we have TWO ADVERBS OF PLACE:
-  ATRÁS- Behind
-  ADELANTE- Forwards
So we now know that the correct option is: ADELANTE due to our need for an antonymous of DETRÁS.