A technical innovation is necessary if we want to keep the grain production______.

A．it allows companies to sell their stocks publicly
B．it doesn't allow companies to sell their stocks publicly
C．it permits one company to own more media businesses at the same time
D．it has eliminated all post-1980 companies

A．used to sell and buy each other in great numbers
B．are trading each other in greater numbers today
C．used to be controlled by two networks -- ABC and NBC
D．have stopped the trend of acquisitions in the 1990s