A student in a science lab is looking at something through a microscope.
A student in a science lab mixes chemicals.
The student who mixes chemicals cannot be using a microscope.
exists e1 x1 x2 x3 x4 x5.(through(e1,x5) & n_microscope(x5) & at(e1,x4) & n_thing(x4) & Actor(e1,x1) & v_look(e1) & in(x1,x2) & n_lab(x2) & of(x2,x3) & n_science(x3) & n_student(x1))
exists e1 x1 x2 x3 x4.(Theme(e1,x4) & Actor(e1,x1) & v_mix(e1) & n_chemical(x4) & in(x1,x2) & n_lab(x2) & of(x2,x3) & n_science(x3) & n_student(x1))