Final answer:
The correct phrase to complete the sentence is 'cruise along', indicating the business is progressing smoothly and steadily after overcoming initial stress and doubts.
Step-by-step explanation:
The correct answer to the sentence 'After the Intel stress and occasional doubts the business begin to cruise _______ with unprecedented results' is C. Along.
When using the phrase 'cruise along', it typically implies that something, such as a business in this context, is continuing in a smooth and steady way.
This phrase is often used to indicate progress without any major obstacles or difficulties. Alternatives such as 'to', 'at', and 'above' do not fit the context of the sentence properly. 'To' suggests a direction towards something, 'at' indicates a specific location or time, and 'above' would suggest superiority over something but not a smooth progression.