Please select the eligibility criteria that correspond to the clinical trial below.
Title: A Phase 4 Randomized, Double-Blind, Placebo-Controlled, Multicenter Study Evaluating The Efficacy And Safety Of Re-Treatment With Varenicline In Subjects Who Are Currently Smoking, And Who Have Previously Taken Varenicline
Brief Summary: The main purpose of this study is to compare the effectiveness and safety of the re-treatment of smokers with varenicline with placebo for smoking cessation during the last 4 weeks of a 12 week course of treatment. The study will also assess whether smokers remain abstinent at Week 24 (12 weeks after the end of treatment) and Week 52 (40 weeks after the end of treatment).


Options:
A: Inclusion Criteria:

1. Has signed the ICF and is able to read and understand the information provided in the ICF.
2. Is 21 to 65 years of age (inclusive) at screening.
3. Smokes at least 10 commercially available cigarettes per day (no brand restrictions), for the last 12 months.
4. Has an expired air CO reading of at least 10 ppm at screening.
5. Is interested in switching to an electronic cigarette.
6. Is willing and able to comply with the requirements of the study.
7. Owns a smartphone with text message and data capabilities compatible with necessary surveys.

Exclusion Criteria:

1. Is unhealthy or cannot participate in the study for any reason (e.g., medical, psychiatric, and/or social reason) as judged by the Investigator or designated medical staff based on all available assessments from the screening period (e.g., safety laboratory, vital signs, physical examination, ECG, concomitant medications and medical history).
2. Has a PHQ-9 score greater than 9, or a score greater than 0 on item #9 ("Thoughts that you would be better off dead, or of hurting yourself in some way") at screening.
3. Has plans to use an FDA-approved smoking cessation product during the study.
4. Has high blood pressure (systolic \> 150 mmHg or diastolic \>95 mmHg) at screening.
5. Has body mass index (BMI) less than 15.0 kg/m2 or greater than 40.0 kg/m2.
6. Has coronary heart disease, structural cardiac disease (including, but not limited to valvular heart disease or cardiac murmurs), cardiac dysrhythmias, syncope, cardiac chest pain, or history of heart attack or heart failure.
7. Has received psychotherapy or behavioral treatments potentially impacting symptoms of depression, anxiety, or nicotine withdrawal within 30 days of screening, or during the study.
8. Is taking antidepressants, psychoactive medications (e.g. antipsychotics, benzodiazepines, hypnotics) or medications that prolong QTc.
9. Has used any of these products in the past 30 days:

   1. Illegal drugs (or if the urine drug screen is positive for cocaine, THC, amphetamines, methamphetamines, or opiates);
   2. Experimental (investigational) drugs that are unknown to participant;
   3. Chronic opiate use.
10. Has used smokeless tobacco (chewing tobacco, snuff), cigars (except for "Black \& Mild" cigars or Cigarillos), pipes, hookah, e-cigarettes, nicotine replacement therapy or other smoking cessation treatments within 14 days of screening.
11. Has a plan to use an FDA-approved quit-smoking treatment in the next 30 days.
12. Is pregnant or nursing (by self-report) or has a positive pregnancy test.
13. Enrollment requirements met.
B: Inclusion Criteria:

* Subjects must have smoked on average of at least ten cigarettes per day during the past year
* Subjects must have no period of abstinence greater than three months in the past year

Exclusion Criteria:

* Subjects with any history of cardiovascular disease
* Myocardial infarction
* Significant arrhythmias
* Poorly controlled hypertension
C: Inclusion Criteria:

* Smokers aged 18 years or above and wanting to stop smoking
* Smokers who have smoked an average of at least 10 cigarettes per day over the last 4 weeks
* Smokers who have tried before to stop smoking at least once with varenicline, and who took varenicline for at least 2 weeks
* The last attempt to stop smoking must be at least 3 months before entering the study

Exclusion Criteria:

* Individuals who have not tolerated varenicline well previously, or who have a current or prior medical or psychiatric history that would make entry into the trial inadvisable
* Individuals who have previously participated in clinical trials of varenicline
* Individuals who have been participating in another smoking cessation trial within the last 3 months, or other drug trial within the last 30 days
D: Inclusion Criteria:

* Participants must have stable, documented cardiovascular disease (including at least one of the following diagnosed \> 2 months prior to the Screening visit - angina, myocardial infarction (MI), revascularization, transient ischemic attack (TIA), and peripheral vascular disease (PVD).
* Participants that smoke \> 10 cigarettes / day.

Exclusion Criteria:

* Participants with unstable cardiovascular disease
* Cardiovascular events in the past 2 months
* Moderate or severe chronic obstructive pulmonary disease (COPD)

Answer: C