Nick's parents suspected that their 20-year-old son might be ...

[saraeharris]

Nick's parents suspected that their 20-year-old son might be addicted to drugs. His behavior was alternately erratic and depressed or highly energetic and loud. Their suspicions were confirmed when he
 
  began receiving phone calls at all hours of the day and night.
  began displaying symptoms of withdrawal.
  seemed to always have a runny nose.
  stayed up until 3 A.M. on most nights and slept until noon.

Question 2

When the absence of a drug creates a craving to satisfy a physiological or psychological need, that is a sign of drug
 
  use.
  abuse.
  addiction.
  overdose.

[nanny]

Answer to Question 1

began displaying symptoms of withdrawal.

Answer to Question 2

addiction.

[saraeharris]

Thank you

[nanny]

No problem