London Underground (subway) platforms are famous for their lively mix of advertisements - witty and amusing, informative, and large enough to be easily read. Ads change every few weeks. Some are part of a series with a story line that slowly emerges for regular commuters although each ad in the series makes sense to the one-time reader. These ads are examples of:
A.
frequency.
B.
opportunistic advertising.
C.
transitional advertising.
D.
transit advertising.
Answer: D