The correct option is
B 465√3required option is not in option It may be typing mistake
Given lines
l1:x−31=y−52=z−71
l2:x+17=y+1−6=z+11
position vector of line l1
→a=3^i+5^j+7^k
position vector of line l2
→c=−^i−^j−^k
normal vector of line l1
→n1=^i+2^j+^k
normal vector of line l2
→n2=7^i−6^j+^k
so line are skews line
SD=∣∣∣(→c−→a)⋅(→n1×→n2)|(→n1×→n2)|∣∣∣
→c−→a=−^i−^j−^k−3^i−5^j−7^k
→c−→a=−4^i−6^j−8^k
→n1×→n2=∣∣
∣
∣∣^i^j^k1217−61∣∣
∣
∣∣
→n1×→n2=^i(2+6)−^j(1−7)+^k(−6−14)
→n1×→n2=8^i+6^j−20^k
|→n1×→n2|=√82+62+(−20)2
|→n1×→n2|=√300
putting →c−→a,→n1×→n2,|→n1×→n2| in formula
SD=∣∣
∣∣(−4^i−6^j−8^k)⋅(8^i+6^j−20^k√300∣∣
∣∣
SD=∣∣∣−32−36+160√300∣∣∣
SD=∣∣∣92√25×4×3∣∣∣
SD=2×465×2√3
SD=465√3
Hence it is correct answer
option A is not correct