안녕하세요?^^
문제를 풀다가 모르는 문제가 있어서...
질문드립니다.

Hold the machine as steadily as you can, ________ it tomorrow.

a. and  you will occasionary put some oil on the drill
b. and you should occasionally put some oil on the drill
c. and occasionally put some oil on the drill
d. and occasionally putting some oil on the drill

정답이 c번이라고 하는데... 왜 그런지 궁금한데.. 답변부탁드립니다.