Approve
@teacherpaul2018📋 You can encourage constructive attitudes in people most effectively by example and reward, and by always ... their good conduct and positive contributions.
🔴 taking notes of
🔵 approving of ✅
⚪️ sanctioning
This is the option that logically fits the sentence the most. "Sanctioning" would be somewhat strange - does one really need to sanction good things? No, they are allowed by default.
"Taking notes of" good conduct could be possible, in the meaning of "I take notes of positive things to reward them later", but since we have the strongest option of "approving of" here, the "taking notes" option is excluded as well.
The thing to remember is that "approve" and "approve of" are not quite the same. Compare these sentences:
"I don't approve of smoking in this establishment" ~ "I don't like smoking here", "I have a negative view on it" etc.
"I don't approve smoking in this establishment" ~ "I forbid smoking in here", "It's not allowed to smoke inside", "I can't/don't sanction it".