Anhydrous aluminium chloride $(Al_2Cl_6)$ is covalent compound and soluble in water giving

Aluminium trifluoride is insoluble in anhydrous $HF$ but dissolves on addition of $NaF$. Aluminium trifluoride precipitates out of the resulting solution when gaseous $BF_3$, is bubbled through. Give reasons.

Given below are two statements :

Statement $I:$ Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green.

Statement $II:$ The green colour observed is due to the formation of copper(I) metaborate.

In the light of the above statements, choose the most appropriate answer from the options given below :

Which of the following is formed when aluminium oxide and carbon is strongly heated in dry chlorine gas