The boy is wondering what to use to clean the microscope lenses. The lens tissue has been treated to prevent scratching. What should one use to clean?

A lens tissue with distilled water (only after removing the loose dust, or else it will scratch the lens), after that lens use lens cleaning fluid/optical cleaning solution or absolute ethanol + lens tissue to remove oily dirt.

(MORE CLEANING DETAILS ARE NECESSARY AND WOULD TAKE AN ESSAY TO EXPLAIN)

the cladogram shown here shows similarities and differences among several classes of vertebrates. anatomically, the four have limb structure as their common ancestor. we might separate the mammals from the other three classes because they a) divergent; do not lay eggs b) identical; are warm-blooded c) varied; a four chambered heart d) homologous; have mammary glands