In the following passage, some of the words have been left out. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
Without habit, personality could not exist, for we could never do a thing twice alike, and ___________ would be a new person each succeeding moment. The acts which give us our own peculiar _____________ are our habitual acts--the little things that do themselves moment by moment without care or attention, and are the truest and best expression of our real selves. Probably _______ one of us could be very sure which arm he puts ________ the sleeve, or which foot he puts into the shoe, first, and yet each of us ____________ formed the habit long ago of doing these things in a certain way.
and yet each of us ____________ formed the habit

Options

A. 1.certain
B. 2.certainty
C. 3.certainly
D. 4.be certain

Explanation

certainly