What are the four ways to avoid a mistake when writing.

Watch your grammer. watch your punctuation! do not rammble on about things that have no relation to the topic of your writting like talking about your girlfriend when your writting about the spanish  inquisition and always KEEP IT SIMPLE. most readers wont be able to comprehend the zenith of your intelligence so dumb it down 

Answer evaporation and condensation;

You need to figure out at which x-value does the graph has a tangent line slope of -1.remember, the derivative is the slope of the tangent line. so find the derivative function and set it to equal -1 to find the x-value that will have a tangent line slope of 0.differentiate with the chain rule.    set the derivative to equal -1 and solve for x.      take log base 10 of both sides. also recall that  .    so the x-coord of the point of tangency is .the y-coordinate of this point of tangency can be calculated using the original function:     using point-slope form, the equation of the tangent line is      the x-intercept of this tangent line is when the graph is at y=0.    this rounds off to  .choice c.