I need help with this question ASAP please :)

When describing down syndrome, it's important to note that a. it can be classified as a single-gene disorder b. it is caused when red blood cells cannot properly form hemoglobin c. it causes infected males to have low testosterone levels d. it is usually caused by three copies of chromosome 21 select the best answer from the choices provided. a b

Acombination reaction is when two or more combine to form one product. a decomposition reaction is when a substance breaks down into two or more simpler substances in a chemical reaction.

A2000 kg car is rounding a curve of radius 200 m on a level road. the maximum frictional force the road can exert on the tires of the car is 4000 n. what is the highest speed at which the car can round the curve?