I wish I could give more points >.< But thank you so much whoever answers all of the questions.

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.