input: Write a python function to check the correctness of a sentence and return a boolean value.
  assert check_correctness("This is a correct sentence.") == True
  assert check_correctness("this is not correct") == False
  assert check_correctness("Another Correct One!") == True
output: def check_correctness(sentence):
      return sentence[0].isupper() and sentence[-1] in ".!?"