Which entity has the principal responsibility to control the execution of processes?
a. operating system
b. process control block
c. memory
d. dispatcher

B)Process control block

Explanation: Process control block(PCB) is the block that is in the form of the data structure containing data and its processing actions. The tasks that come under the PCB are controlling the data in block, entering the data in table, processing the data etc.

The other given options are incorrect because operating system is the system on which the whole processing of task are done, memory stroes the data and dispatcher is the data dispatching unit .So , the correct option is option(B).

answer: internal fragmentation is the difference between the (fixed) size of a memory hole and the data within in that memory. for example, if a 1,024 byte block of memory holds 800 bytes of data, then the 224 bytes difference is considered lost to internal fragmentation.

external fragmentation occurs when the sum of memory fragments is large enough to satisfy a request, but the holes are non-contiguous and the request cannot be satisfied. this can occur when memory is dynamically allocated and freed.

explanation: