听力原文： Farmers usually use plows to prepare their fields for planting crops．Plows cut into the ground，and lift up weeds，and other unwanted plants．However，plowing is blamed for causing severe damage to top soil by removing the plants that protect soil from being blown or washed away．Many farmers in South Asia are now trying a process called Low Till Farming．Low Till Farming limits the use of plows．In this method of farming，seeds and fertilizer are put into the soil through small cuts made in the surface of the ground．Low Till Agriculture leaves much or all the soil and remains of plants on the ground．They serve as a natural fertilizer and help support the roots of future crops．They take in rain and allow it to flow into the soil instead of running off．It has been proved that Low Till Farming increases harvests and reduces water use，and this method reduces the need for chemical products because there are fewer unwanted plants．Scientists say Low Till Fanning is becoming popular in South Asia，which is facing a severe water shortage．They say the area will become dependent on imported food unless water is saved through methods like Low Till Farming．Currently，more than 150 million people in South Asia depend on local rice and wheat crops．Farmers grow rice during wet weather．During the dry season they grow wheat in the same fields．Farmers are using the Low Till Farming method to plant wheat after harvesting rice．Scientists say Low Till Agriculture is one of the best examples in the world of technologies working for both people arid the environment．
What is the main problem caused by the usual way of plowing？

A. The crop's blooming period is delayed.
B. The roots of crops are cut off.
C. The topsoil is seriously damaged.
D. The growth of weeds is accelerated.