ANS:B - 5

In general, a metric chain has a 10 cm link length for a meter length.
So, the answer should be 10. 20 meter length = 100 links.
1 meter length = 100/20 links.
= 5 links. This is for 30 m chain.
For 30 m chain = 150 links,
Therefore , 1 m = 5 links,
And for 20 m chain = 100 links. First, assume itis 20 m chain. Each link 0.2m. So, total no of links in 20 m chain is ={20/0.2)=100.
Therefore no of links per m length is=(100/20)=5. 5 is correct because each link is provided after 20cm or 0.2 m. So, if we count manually also from starting of the chain then we will get 5 links per metre.