According to Christopher McKay, the possibility of transforming Mars______.

A．is essential to the efficient control of weeds
B．may lead us to be aware of the fact that the soil contains enormous quantities of seeds of numerous species
C．helps us to have a good idea of why seeds can lie dormant for years
D．provides us with the means to identify weeds at the seedling stage

A．depends on climate and soil type in a virgin environment undamaged by human beings
B．was greatly affected by human beings before they started using chemical substances on the soil
C．was radically transformed by uncivilized human beings
D．refers to plants, trees, climate, type of soil and the ecological environment