(B) II and III only
Given IP address space: $202.61.0.0/17$, $17$ bits are in network ID bits(NID) and rest will be host ID bits(HID).
$\underbrace{202.61.0}_{17 \text{ NID } bits}0000000.00000000$
In order to assign $1500$ hosts we need minimum $11$ bits
$\underbrace{202.61.0}_{17 \text{ NID } bits}\ \underbrace{0000}_{4 \text{ SID } bits}\underbrace{000.00000000}_{11 \ \text{ HID } \ bits}$
We have $4$ subnet bits, eligible networks are those which belongs among possible 16 subnets.
If we expand the given Network bits we can see:
- $202.61.\textbf{84}.0/21 = 202.61.0\textbf{1010}100.0$
Not possible as all Host Bits should be zero
- $202.61.\textbf{104}.0/21 = 202.61.0\textbf{1101}000.0$
Possible
- $202.61.\textbf{64}.0/21 = 202.61.0\textbf{1000}000.0$
Possible
- $202.61.\textbf{144}.0/21 =202.61.1\textbf{0010}000.0 $
Not possible as $16^{th}$ bit from right (part of $\text{NID}$ is $0$ and not $1)$