Please help its 6th grade science

Describe the primary and secondary immune response in terms of speed and number of antibodies produced?

What happens when the cell copies its chromosomes

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2