Common nouns include both abstract as well as concrete nouns. These
nouns name things, whether abstract or concrete. By abstract we mean,
something that can be sensed or felt, and not touched. They include
emotions and states of being.
Proper nouns name a specific person, place or animal, for e.g. Amy, America. Proper nouns always begin with a capital letter.
Option C: 'Wisdom' means 'the quality of having good experience and knowledge'.
'Strength' means 'the state of being strong'.
These are qualities and cannot be perceived through any of our senses. Hence they're both abstract. So, option C is correct.
Option A: 'Wisdom' is a common noun but more specifically, it's an abstract noun. Hence this option is not as suitable.
Option B: 'Wisdom' refers to a state of being wise and it does not name a specific thing or a person. Also, it does not begin with a capital 'W' as proper nouns should. Hence B is wrong.
Option D: 'Strength' is a common noun, but this option does not identify the second noun, 'wisdom'. Also, 'strength' is more specifically an abstract noun. Hence D is wrong.