I still can't understand the meanings for 'call on'
- officially ask someone to do something
- ask a student a question
- decide to use something
- produce a quality
- ask someone to prove statement
- visit someone for short time
Could you give examples and logical conjectures of 'call on' for 3 and 4 cases?
Macmillan's dictionary gives an example for 4:
She called on all her reserves of courage to face the ordeal ahead of her.
and then gives Synonyms and related words
affect, shape, impact...
I can not understand why these words are synonyms, especially affect and impact?
For meaning 3 Macmillan's dictionary gives this example
We may need to call on professional help.
and gives Synonyms and related words - repurpose, use, bring in...