Which of the following components of cement sets at the slowest rate?

Which one of the following is a covalent crystal?

'Stability of a crystal is reflected in the magnitude of its melting points'. Comment. Collect melting points of solid water,ethyl alcohol,diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?

$MnO$ is $:$

Which of the following is $NOT$ a property of solids?

Identify the covalent crystal from the following.