Changes in the trilobite exoskeleton can be attributed to

Where do homologous chromosomes exchange genetic material through crossing over?               a.  chlorophyll    b.  centrosomes    c.  centromeres    d.  chiasma

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

In response to framton's dialogue about his health issues, mr. sappleton replies: "no? " said mr. sappleton, in a voice which only replaced a yawn at the last moment. then she suddenly brightened into alert not to what framton was saying. what does this statement reveal about how mrs. sappleton feels about framton? a) she finds him boring. b) she's happy he came by. c) she finds him annoying. d) she feels sorry for him