According to the census results of a city, the number of single men over the age of 35 is 1.5 times that of single women over the age of 35. Obviously, unless some of these men marry foreign women as wives, some of these single men will be forced to maintain Single status. What assumptions are the above conclusions based on? ['These single men have the concept of "starting a business before getting married".', 'There are more single women working outside the city.', 'These single men are unwilling to marry women older than them.', 'These single men tend to marry women of their age.']