It is A. The HL theorem works when the hypotenuses of two triangles, and another leg, are the same. For these two triangles the hypotenuses are clearly the same, so we need to know if they have two corresponding equal legs. OM and ON are two corresponding legs, and if these are equal the HL theorem will work. So, the answer is A.
It would take her 10min to finish 35 hot dogs because 21 divided by 6 equals 3.5 so in six minutes she eats 3.5 hot dogs per minute. Multiply 3.5 by ten you get 35