The sentence about the technicians is the tricky part.
No technicians are lab assistants, but the some or all technicians may or may not be archeologists/scientists. You’ve been told
nothing about the relationship between technicians and archeologists/scientists, so there may or may not be overlap. Do not assume
anything about this relationship!
If you note that you know nothing about the relationship between technicians and archeologists, you can eliminate answers (F) and
(G), since both deal with this relationship. (H) is too extreme. You know that at least one lab assistant must be an archeologist. This
does not mean that all lab assistants are scientists. (J) is also too extreme. There is no reason to deduce that all archeologists (at the
dig or otherwise) are lab assistants. This leaves you with (K), which is correct. Some scientists must be lab assistants since there is
an overlap between the two groups.