D. worked out
Feedback work out - 1. to plan 2. to understand 3. to cost 4. to improve 5. to exercise.
put by - to save money in order to buy something.
throw together - 1. to make something quickly 2. to make people meet.
pick up - 1. to lift something or somebody up 2. to tidy something 3. to get something 4. to collect 5. to learn 6. to notice