Explanation

Since the last part of the sentence mentions the problem of disposing of old equipment, it is likely that the three-year-old personal computer described by Blank
(ii) will be characterized by a word that suggests why it is being disposed of. Neither “familiar” nor “inestimable” suggests something that needs to be cast off, while “outdated” does; therefore, it is the correct response. Since the outdated three-year- old computer is presented as an example of the trend in technology mentioned in the first part of the sentence, Blank (i) must be completed with a word that characterizes this outdatedness. “Obsolescence” does exactly that, so it is the correct response. Neither “affordability” nor “complexity” is exemplified by computers that become quickly outdated, so they are incorrect. Thus the correct answer is obsolescence (Choice C) and outdated (Choice D).
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Sir
Here ,can't "complexity" be used for the first blank since technological complexity will lead to outdatedness as explained in the example? Please explain.

No.

Simply because the on-going of the question is in the same direction. Considering that the second blank is outdated (computer related) the first one must be the obsolescence and not complexity.

Hope this helps
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Why couldn't it be A ?

With the rate of technological affordablity accerelating , people have less price to people for tech and they consider the PCs to be outdated afer 3 years ?
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dispose of old equipment is no small matter.
is the key word here

Obsolete and outdated are synonymous
Thus CD