Interstellar matter blocks our view of the disk of our galaxy: a. not at all at any wavelength.
b. more-or-less equally at all wavelengths of radio waves to light waves.
c. most at radio wavelengths, where hydrogen absorbs radio waves efficiently, and least at optical wavelengths.
d. more at optical wavelengths, less in the infrared, and not at all at radio wavelengths.

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.