Please help
which ones???

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

Convert .347 kilometers to miles show your work

How does a catalyst increase the speed of a reaction? a. the catalyst eliminates the activated complex stage, allowing products to form immediately. b. the catalyst lowers the energy level of the reactants, making it easier for them to react. c. the catalyst makes it easier for the activated complex to form, lowering the activation energy. d. the catalyst raises the energy level of the products, making the reaction finish sooner. reset next