Pollution Levels in Lake Erie Have Been Modeled by the Equation

Multiple Choice

Pollution levels in Lake Erie have been modeled by the equation , where x is the volume of pollutants (in cubic kilometers) and t is the time (in years) (Adapted from R. H. Rainey, Science 155 (1967) , 1242-1243) . Find the initial pollution level; that is, find x when t=0. ​

A) 0.23 km³​
B) 0.2 km³​
C) 0.40 km³​
D) 0.10 km³​
E) 0.8 km³​