65.
Your Answer is
Correct Answer is B
Explanation
Here we want to express the density of cranes.
Item B: The concentration "density" is correct. English interpretation: a large amount of something in a particular place or among particular people.
A item: heap (messy) a bunch of things, the semantics do not match.
Item C: A string of bunches, none of which match the semantics.
Item D: The supply supply does not match the semantics.