Can someone explain to me how to answer this please?

Which of these is not an example of chemical weathering? a. iron-rich mineral rusting b. feldspar turning into clay c. limestone reacting with acid d. granite breaking up into sand

What is the percent by mass of oxygen in fe2o3

If a simple machine aduces the strength of a force, what must be increased? the speed of the input force the work the simple machine performs the size of the simple machine the distance over which the force is applied