The sentence But constant negativity can also get in the way of happiness, add to our stress and worry level and ultimately damage our health.' (l. 02-04) could be paraphrased only by the following: 
The word help (l. 17) may be both a noun and a verb without having to change its spelling. The same may occur to all the words bellow, EXCEPT for: 
In the sentence taken from the text: The ability to recognize hand poses, for instance, will make it possible for people to interact with computers in new and more natural ways, such as communicating with computers simply by pointing at things, the underlined expression introduces: 
In text 9A2CCC, the word their (l.15) refers to 
The word from is used in the first sentence of text 9A3AAA to specify 
Based on the text, judge the following items.
Both Besides and Furthermore can be used instead of In addition (line 2).
Based on the text, judge the following items.
If we want avoiding is a suitable alternative for If we want to avoid (line 4).
Based on the text, judge the following items.
The idea expressed by should in we should inform the population (lines 4 and 5) can also be expressed by ought to.
Based on the text, judge the following items.
In line 8, the s in diets is pronounced as the s in foods.
In text I, without altering the meaning of the sentence, the noun realms (l.35) could be replaced by (mark right C or wrong E):
domains.