Why is it dangerous to take more than one drug at the same time, especially when alcohol is involved?

• Drugs may counteract each other's effects.
• Drugs may have a cumulative effect, leading to increased impairment, especially with alcohol.
  Explanation:

  "Taking more than one drug at the same time is even more dangerous since drugs may have a different overall cumulative effect, especially when alcohol is involved."
• It is only dangerous if the drugs are illegal substances
• It is not dangerous at all.