Semi-conductors are materials that a) are good conductors. b)allow electron flow and resist neutron flow. c)have insulator and conductor properties. d)allow neutron flow. semi-conductors are materials that have insulator and conductor properties.

c)have insulator and conductor properties.

Explanation:

Semiconductors, as the name suggest have properties of both insulators and conductors. Until the current/voltage applied to them reaches a particular threshold they work like an insulator. Once the threshold is crossed they behave like a conductor. This property makes them very useful in electronic devices. In fact almost all the electronic equipment in today's age use semiconductors in some way or the other.

the total distance traveled by the car is

30km + 49km = 79 km .