In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
Swollen joints (1)_______ when there is fluid in the tissues around the joints. It can be very (2)_______ and can make it difficult to move the affected joints. In some cases, swelling may cause affected joints to increase in size or appear to be an odd (3)_______. Joint pain and swelling can affect more than one (4)______ at a time. The most common joints to be (5)______ by pain and swelling are elbows, wrists, shoulders, the base of the spine, knuckles, hips, knees or ankles.

Select the most appropriate option to fill in blank number 1.