When S strain bacteria were killed by being heated to 60C, then mixed with live strain bacteria and injected into mice, a greater % of mice died than when the strain bacteria were heated to 100C. Can you propose an explanation for these observations?

Due to live strain bacteria.

Explanation:

The first method cause more damage to the mice as compared to the second method because in the first method the killed bacteria were mixed with the live strain bacteria. This live strain bacteria causes diseases in the mice and eventually killed the mice while on the other hand, all the bacteria were killed due to very high temperature so that's why first method causes more damage than second one.

it has one origin of replication, but it proceeds in two directions - d)