The formula for LA is 

. Right now we only know the height but we need to know the slant height so we can set up a triangle inside the cone (look at attached image). The slant height is the hypotenuse. Solving for it we get 

. Now we can plug everything we have into the formula: 

. This means LA is 

 but that's not one of the options even if i turn it into a decimal so recheck my work but I'm pretty sure this is the answer.