sandy's homework she can't solve

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

bool isValidInput(const int numArgsNeeded, const int numArgsRead, const bool isLastElementOnLine) {
  char lastCharacterOnLine;
  bool correctFormat = (numArgsRead == numArgsNeeded);
  if(isLastElementOnLine) {
    scanf("%c", &lastCharacterOnLine);
    correctFormat = correctFormat && lastCharacterOnLine == '\n';
  }
  return correctFormat;
}

char getValidChar(const bool isLastElementOnLine) {
  const int numArgsNeeded = 1;
  int numArgsRead;
  char theCharacter;
  numArgsRead = scanf(" %c", &theCharacter);
  if(isValidInput(numArgsNeeded, numArgsRead, isLastElementOnLine)) {
    return theCharacter;
  }
  else {
    printf("Invalid formatting. Ending program.\n");
    exit(0);
  }
}

double getValid(const bool isLastElementOnLine) {
  const int numArgsNeeded = 2;
  int numArgsRead;
  double tempValue;
  char tempUnit;
  numArgsRead = scanf("%lf %c", &tempValue, &tempUnit);
  if(isValidInput(numArgsNeeded, numArgsRead, isLastElementOnLine)) {
    return tempValue && tempUnit;
  }
  else {
    printf("Invalid formatting. Ending program.\n");
    exit(0);
  }
}

char getNewUnit(const bool isLastElementOnLine) {
  const int numArgsNeeded = 1;
  int numArgsRead;
  char newUnit;
  numArgsRead = scanf(" %c", &newUnit);
  if(isValidInput(numArgsNeeded, numArgsRead, isLastElementOnLine)) {
    return newUnit;
  }
  else {
    printf("Invalid formatting. Ending program.");
    exit(0);
  }
}

int main() {

  char conversionChoice = 0;
  char newUnit = 0;
  double originalValue = 0;

  printf("Pick the type of conversion that you would like to do.\n");
  printf("T or t for temperature\n");
  printf("D or d for distance\n");

    printf("Enter your choice: ");
    conversionChoice = getValidChar(true);
  if (conversionChoice == 'T' || conversionChoice == 't') {
    printf("Enter the temperature followed by its suffix (F, C, or K): ");
    originalValue = getValid(true);
    printf("Enter the new unit type (F, C, or K): ");
    newUnit = getNewUnit(true);

  }
  else if (conversionChoice == 'D' || conversionChoice == 'd') {
    printf("Enter the distance followed by its suffix (I,F,Y,M): ");
    originalValue = getValid(true);
    printf("Enter the new unit type (I,F,Y,M): ");
    newUnit = getNewUnit(true);
  }
  else {
    printf("Unknown conversion type %c chosen. Ending program.", conversionChoice);
    exit(0);
  }

  return 0;
}