Final answer:
The instruction 'entry 30' loads the value 50 into the accumulator in a one-address machine, which references the value stored at memory address 30.
Step-by-step explanation:
In a one-address machine with an accumulator, stating that an entry 30 means the machine would perform a load operation of the value stored at memory address 30 into the accumulator. According to the data provided, word 30 contains the value 50. Therefore, executing the entry 30 instruction would result in the accumulator containing the value 50.
Regarding the 'complement of the entry' mentioned in part c, it generally refers to taking the binary inverse of a given number in a digital computer system, which turns all 0s into 1s and all 1s into 0s. However, without specific instructions or contextual numbers provided, a precise answer cannot be formulated for what the complement would be in this particular case.