Why are there so many problems with drivers?

a. many variations in hardware, slightly differing implementations, conflicts.

b. programmers do not care about quality.

c. driver code should be the same for all hardware.

d. drivers must be always included with the operating system, never forced into the os.

Ibelieve it would be c

Function tipcalculate (slider, bill){  var tip = document.getelementbyid('tipamount');   var slideval = document.getelementbyid('slideval');   var bill = document.getelementbyid(bill).value;   var prcnt = slider * .01;       if (bill == null || bill == '') {      tip.innerhtml = ' enter an amount';       return false;   }  if(isnan(bill)) {      tip.innerhtml = ' enter a number';       return false;   }  if(bill > = 0){      tip.innerhtml = '$' + (bill * prcnt) .tofixed(2);   slideval.innerhtml = slider + '%';   }}