The work function for sodium surface is 2.0 eV and that for aluminum surface is 4.2 eV. The two metal are Illuminated with appropriate radiation so as to cause photoemission. Then

• A. the threshold frequency for sodium will be less than that for aluminum  
• B. the threshold frequency for sodium will be more than that of aluminum
• C. both sodium and aluminum will have the same threshold frequency  
• D. none of the above