Answer:
To create a medium for the reaction since it occurs in acidic medium
Answer: Mercury-194 is an unstable isotope and hence is radioactive.
Explanation: Mercury-194 is an isotope of mercury, having formula 
Number of protons in this isotope = 80
Number of neutrons in this isotope = 114
This isotope is radioactive in nature and under decay process by Electron Capture.
Electron capture reactions are the reactions in which a proton in a nucleus absorbs an electron and convert it into neutron. The resulting nucleus will have a decreased atomic number and same atomic mass.
Reaction for electron capture of mercury-194 follows:

Hi,
You didn't mention what "the following" were - please add additional information so the problem can be solved.
(I posted the picture for a ray diagram and the first law of reflection.) The rays show the first law of reflection since everything gets reflected. Look at the picture for more: