The Braess paradox shows that: O a. the total travel time increases when improving the network, because more travellers are attracted to travel on the network b. the total travel time increases when improving the network, because travellers are selfish C. the total travel time increases when improving the network, because travellers cannot improve their travel cost unilaterally by changing their route the total travel time increases when improving the network, because travellers look for the system optimum e. the total travel time increases when improving the network, because more travellers use the new route