In a dual$-$threaded core with two levels of scheduling, as shown in Figure $5\mathrm{.}15,$ the:

Question $4$Answer

a$.$

Second level $($core scheduling$)$ determines how the core fetches instructions from memory for execution.

b$.$

First level assigns priorities to software threads, and the second level uses a round$-$robin approach on hardware threads.

c$.$

First level $($operating system scheduling$)$ assigns software threads to hardware threads $($logical CPUs$).$

d$.$

Second level is not relevant to the operating system, as it only manages software threads.