As result as follows these two network addresses can be assigned to the network containing 10 hosts:
B. 10.18.10.208/28
C. 10.18.10.224/28
Explanation:
Since 10.18.10.0/24 depends on subnet also. 10.18.10.0 To 10.18.10.63 is taken to leftmost network address. Since it is 4 host bits, it required to accommodate 10 hosts. And it marks to be in end with /28.
And more over 10.18.10.200/28 should be invalid network number. Moreover other one ends with /27 it is invalid to this specific ranges of tcpip address.
Other 10.18.10.200/27 or 10.18.10.224/27 is falls in invalid range, because it ends with /27
