roots are a vehicle for absorbing water and nutrients from soil into the plant & if something is a vehicle for a process then that something performs that process ->  roots absorb water and nutrients from the soil  roots absorb water and nutrients from the soil & absorbing is a kind of function ->  the function of roots is to absorb water and nutrients  the function of roots is to absorb water and nutrients & some minerals are nutrients -> the function of roots is to absorb water and minerals