Restriction enzymes cut the strand of DNA a little away from the center of the palindrome sites, but between the same two bases on the opposite strands. This leaves single stranded portions at the ends. There are overhanging stretches called sticky ends on each strand. This stickiness of the ends facilitates the action of the enzyme DNA ligase. In the given question, option A and C will produce sticky ends while option B and D will produce blunt ends.

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