Answer: c. the wavelength of both transverse and longitudinal waves is measured parallel to the direction of the travel of the wave.
Explanation:
The wavelength is simply the distance that takes place between two successive troughs fir a particular wave. It is calculated as:
Velocity / Frequency.
From the statement given, the option that is accurate is that the wavelength of both transverse and longitudinal waves is measured parallel to the direction of the travel of the wave. 
 
        
             
        
        
        
Excess Nitrates in the water supply
        
             
        
        
        
NaCl is dissolved in water so that in a given region or volume the concentration is initially higher in one part than the other l, thus simple diffusion will occur so that there is a net difference or 0, with respect to the concentration of NaCl in a particular volume of water than another. Basically the NaCl will be distributed throughout volume of water.