Which of the following statements regarding two STATA commands is incorrect ? gen crowded=0 replace crowded=1 if population>=1,000,000

a) Instead of these two commands, the same result is obtained with the following single command: gen crowded = population>=1,000,000
b) The first command is incorrect. it should have been gen crowded==0
c) If two commands are run, the crowded variable will take the value 1 for observations without population information (missing obserbations).
d) Running two commands creates a dummy variable crowded showing observations with a population of less or more than one million.