Elements in the same period have . the same number of protons
the same number of electron shells
similar properties
the same number of electrons

The answer for #3 is c but i don't know why

For the following dehydrohalogenation (e2) reaction, draw the zaitsev product(s) resulting from elimination involving c3–c4 (i. e., the carbon atoms depicted with stereobonds). show the product stereochemistry clearly. if there is more than one organic product, both products may be drawn in the same box. ignore elimination involving c3 or c4 and any carbon atom other than c4 or c3.

Determine the reaction and balance the following equations urgent due in the morning