The "Lookup()" function should give you the results needed. This will allow you to send to any list or data extension and pull back records from a completely different data extension. In order for this to work, your Unique Subscriber ID on the Lookup DE would need to relate back to the subscriber you're sending to. For example, if your Specific ID matches up with Subscriber Key on your account, you can setup something similar to the below.
More info can be found here as well: Data Extension Ampscript Functions
The below creates 3 variables. "SubscriberAnswer" does your lookup to pull the value from your other data extension. This says, pull the answer from the row of data where the Column "UniqueID" matches the value of "_SubscriberKey" for the subscriber being sent to. I've added the variable "Survey" to generate a standard response when their answer is not null. Then I perform an IF/Then statement in the variable "Answer" to say, If the variable "SubscriberAnswer" is null, pull back "Please fill out Survey", otherwise just pull back the value for "SubscriberAnswer". Hope that is clear and useful. Thanks!
Var @SubscriberAnswer, @Survey, @Answer
Set @SubscriberAnswer = Lookup("Survey","Answer","UniqueID",_subscriberkey)
Set @Survey = Concat("Thank You. Your results can be found here:", " ", @SubscriberAnswer)
Set @Answer = IIF(Empty(@SubscriberAnswer), "Please fill out Survey", @Survey)