Carbon dioxide, and Sulfur dioxide, because you have to know what gas are very dangerous and which ones arent........
Answer: embryo
Explanation:
An embryo is the early stage of the development of the diploid cell called as zygote. It is formed by the continuous cell division and differentiation of the zygote. It is the unborn offspring which is in the state of development. In humans the embryonic state remains from second to eighth week after the process of fertilization. After eighth week the embryo is called as fetus.
According to the given situation, the six weeks of pregnancy is indicative of embryonic state.
This is heavily disputed, and honestly, it varies on a person-by-person basis. Some people are visual learners (so it's effective for them to use videos and pictures to help them study), some prefer being hands-on, etc...
Generally though, I'd say the most effective method that works for most people is through visceralisation. This is the process of associating concepts, words. phrases etc. with your different senses (sound, touch, images...). You can read up more on it by searching up "visceralisation for studying".
Unusual irritability, ocd and im sure in some cases ptsd