Where would the following activity best fit on the physical activity pyramid?
yoga
a. sedentary activities
b. flexibility activities
c. aerobic activities
d. lifestyle activities

Yoga would best be characterized as a flexibility activity - b.

Yoga is, however, also considered to be a lifestyle activity as well - for obvious reasons. It carries along a lot of different things which one person could do, apart from yoga which can be found in the same "conceptual" world. 

However, yoga is primarily a flexibility activity.