Exercise 2. Сделайте предложения отрицательными

1. You have been writing a report since morning.

2. We have been working in the garden for three hours.

3. I have been typing letters since ten o’clock.

4. Tom has been running for twenty minutes.

5. A cat has been sitting in the tree for an hour.

6. Jane has been studying English for two years.

Baobab - a kind of tree.  baobab - one of the thickest tree in the world.  the average circumference of the barrel in the baobab is 9-10 meters, with the height of the tree is in the range of 18-25 meters and the diameter of the crown reaches 40.from october to december baobab blossoms.  flowers in the baobab large, white with five petals.  they are disclosed in the late afternoon and last only one night.  in the morning the flowers wither, acquiring an unpleasant putrid odor, and fall off.following the developing fetus, which resemble cucumbers coated with a thick hairy skin.  inside the fruit are filled with pulp with black seeds.  the fruits are edible.because of addiction to them baobab monkey called "monkey bread tree."the average life expectancy of baobab "only" 1,000 years.local residents have been used almost every part of the baobab.  from its rough bark produce fiber for the manufacture of fishing nets, ropes and fabrics.  from the ashes of the bark of baobab are quite effective medicine against colds, fevers, dysentery, heart disease, asthma, toothache, insect bites.young leaves are added to salads, used as dry spices.  young shoots are boiled like asparagus.flower dust used to make glue.baobab - a treat for elephants.  african giants eat them almost entirely, not just the leaves and branches, and trunk. the oldest baobab 6,000 years    

1. i exercise regularly in summer but more to do in winter. 2. she usually walks slowly but now she is walking even   faster . 3. nina speaks loudly but mary speaks even   louder . 4. he runs fast, than other boys. 5. i don’t sleep enough, less   than 8 hours. 6. he behaves badly, than other boys. 7. i smile often, more than my sister. 8. peter lives far from school, but ann lives closer .

я думаю, что  4 и в 6 предложениях ничего изменять не надо. может я ошибаюсь.