Group of teen males picking up garbage.
A group of teenagers clean up garbage for extra credit.
Just because a group of teen males is picking up garbage doesn't mean they are doing so for extra credit.
exists e1 s1 s2 s3 x1 x2 x3.(ne_org_group(s1) & a_topic(s1) & of(s1,x1) & a_up(s3) & Manner(e1,s3) & Theme(e1,x3) & Actor(e1,x2) & v_pick(e1) & n_garbage(x3) & (x1 = x2) & n_male(x1) & a_teen(s2) & Theme(s2,x1))
exists e1 s1 s2 x1 x2 x3 x4.(a_up(s2) & Manner(e1,s2) & Theme(e1,x3) & Actor(e1,x1) & v_clean(e1) & for(x3,x4) & n_credit(x4) & a_extra(s1) & Theme(s1,x4) & n_garbage(x3) & of(x1,x2) & n_teenager(x2) & n_group(x1))