Professor: Now when I mention the terms "boom and bust", what does that bring to mind?
Student: The dot-com crash of the 90s.
Professor: OK. The boom in the late 1990s when all those new Internet companies sprang up and were then sold for huge amounts of money.
from TOFEL TPO6 Listening
This is a part of a lecture in an economics class.
The subject is 'The boom', but I can't find a verb. why?
Can I use this sentence in writing? Or is it only used in speaking?