Calcium carbonate is indeed used as an antacid (among Mg(OH)2, Al2(OH)3 and NaHCO3).
Ferrous oxide or Iron (II) oxide is a dark substance, and I would certainly think twice before using a dark tooth paste (Yew! ) It might even rust if left in the mouth for some time!
Answer:
the answer would be the first one, gamma decay
I'm pretty sure number 48 is C. Hope this helped :)
Cattle contribute to more carbon emissions than all of the worlds transport.
Plants :)
Hope this helps!