The nurse is performing an admission assessment on a client. The client states that she has been smoking two packs of cigarettes a day for 20 years. The nurse would chart how many pack years for this client?

Number 4 is correct.

Rationale: A pack year is one pack of cigarettes smoked daily for one year. This client smokes two packs per day. The calculation is 2 (packs per day) × 20 (years smoking) = 40 pack years. The other calculations are incorrect for this client.