Capitalism has remained the same for the past 100 years.
a. true
b. false

Capitalism indeed has not stayed nor remained the same for the past 100 years - false. 

Capitalism has been slightly changing all the time for the past 100 years with minor modifications going on continuously. So no, it is not true that capitalism hasn't changed with time. 

I say D because “We must work hard in order to fix our bad habit” makes the most sense.