Para Completion:

• If the missing line is the last line of the paragraph, it should complete the chain of thoughts that are being expressed in the paragraph
• The last line need not necessarily be a summary of the paragraph but it must necessarily follow the line of thought being expressed in the paragraph and complete that chain of thought
• While solving para completion questions remember to find the chain of thoughts running through the paragraph. Two common constructions of paragraphs are firstly, starting with an analogy or illustration and then tying in with the general concept and secondly, introducing the general concept and then forwarding arguments or illustrations in favor of the same. Hence, the last line of the paragraph must always state some conclusion about the general concept - a conclusion that follows either from the illustration/analogy or from the arguments made in favour of the concept.
• If the missing line is not the last line - find the option that connects the thought being expressed just before and just after the missing line