2 more

[belly_ttt]

1) Beware of the dangerous deep hole ahead
or
Beware of the dangerously deep hole ahead
?

And in case both are acceptable, what is the difference between them?

2) Here is an excerpt from the "Your relativistic brain "- Speed Reading Book- Tony Buzan

If you were driving along a motorway at 100 miles per hour and your partner suddenly covered your speedometer and asked you to decelerate to 20 miles per hour, at what speed do you think you would level off, saying" That's 20 miles per hour"

Most people estimate between 40 and 60 miles and are correct

What does are correct mean here? Nobody asked any question

3) What is the difference between excerpt and extract?

[Soup]

1a) Beware of the dangerous, deep hole ahead.
=> the hole is both dangerous and deep. Note that, the comma represents an omitted conjunction: the dangerous and deep hole ahead.

1b) Beware of the dangerously deep hole ahead.
=> the depth of the hole is dangerous. The adverb dangerously modifies the adjective deep.

2) Ellipsis:

Most people estimate between 40 and 60 miles and [they] are correct [in their estimation].

3) Extract means to draw or pull out, and when it refers to removing something for separate consideration or publication it's synonymous with excerpt.