Well you know that you have to balance out the equation to 0. So if I is -1 and Ca is +2 you know that I had to equal to -2. So you can do that by having two of them. So Ca=+2 and I2=-2 so CaI2 would equal 0 meaning that would be the correct answer. Hope that I explained that correct :)
When phosgene is reacted with an excess of methanol, this produces dimethyl carbonate. Dimethyl carbonate is used in methylating anilines, phenols, and carboxylic acids, and is also being studied for its use as an alternative additive in fuel.
The industrial production of dimethyl carbonate no longer uses phosgene because of the latter's toxicity. Phosgene widely gained infamy when it was used in chemical warfare during WWI.
Answer:
See the picture... I hope that's the answer