While at the Dentist, Six-Year-Old Alex Listens as His Mom

While at the dentist, six-year-old Alex listens as his mom tells the dentist she flosses her teeth daily. Alex notices that the dentist complimented his mom on her behaviour. As a result of this brief encounter, which of the following would predict that Alex will develop a favourable attitude toward flossing?

A) operant conditioning
B) observational learning
C) classical conditioning
D) appetitive conditioning