The correct option is C There were lot of adjustments to be made.
As we go through the passage we understand that it was difficult to take selfies in the early 20th century because "the whole process was so slow that Cornelius had time to uncover the lens, run into the shot and then go back to cover the lens". The entire process of taking a self-portrait therefore required a lot of time and adjustments. Hence option C is the correct answer.
Options A, B and C are not the correct answers to this specific question.