1) B
(I'm not so sure of this one) All of the other options have a steady impact on population regardless of the density of organisms except competition
2) D
Increased carbon dioxide levels would not hinder plant growth, and tsunamis aren't really linked to carbon dioxide levels. Increased carbon dioxide is unlikely to lower the air temperature so only D is left.
3) A
4) Three properties of water that allow it to sustain life are that it is adhesive, it is a good solvent, and cohesion. Adhesion is important in situations such as water travelling up xylem tubes in plants so that the water is not pulled down by gravity and can reach parts of the plant that need water. Cohesion allows the water being pulled up the xylem to stay together and for water molecules to be pulled when a neighbouring one is moved. Water being a good solvent allows inorganic minerals to be taken with water through vascular tissue, such as in the previous example.
The answer should be C, progesterone.
Progesterone is the hormone which can help maintain the lining of uterus and to further thicken it so that the uterus is prepared for implantation and the development of a baby. The level of progesterone is significantly rose after ovulation.
On the other hand, LH, luteinising hormone, is produced by oestrogen, another female hormone which will drop after ovulation. LH helps stimulate ovulation and prevent the development of other follicles, the origin of eggs, to form yellow body instead. Which yellow body is the one which stimulates the production of progesterone.
Last but not least, I believe D should be testosterone, and it is a male hormone so it will not be found in female normally.
Therefore, your answer should be C, progesterone.
