Which of the following is a linear molecule?

Among the following,which is water insoluble?

Graphite is a soft solid lubricant and is extremely difficult to melt. What is the reason for this behavior of graphite?

Electrons ejected from the surface of a metal,when light of certain frequency is incident on it,are stopped fully by a retarding potential of $3 \ V$. Photoelectric effect in this metallic surface begins at a frequency $6 \times 10^{14} \ s^{-1}$. The frequency of the incident light in $s^{-1}$ is : [Planck's constant $= 6.4 \times 10^{-34} \ J \ s$,charge on the electron $= 1.6 \times 10^{-19} \ C$]

Which one of the following is a slime mould?

Golgi bodies are absent in . . . . . . .