I would say by putting two fingers under your chin or putting two fingers on the back of your wrist, hope i helped ! :)
Answer:
Photosynthesis
Explanation:
Studies about the time period of oxygen accumulation suggests that free oxygen was first produced by prokaryotic and then later by eukaryotic organisms in the ocean. These organisms carried out photosynthesis more efficiently, producing oxygen as a waste product.
The organism mainly responsible for this is known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, oxygen.
Answer:

Explanation:
The ratio of pressure 2 to 1 us 5.48/1= 5.48 rounded off as 5.5.
Referring to table A.2 of modern compressible flow then 
Also
and making
the subject of the formula then
Making reference to
diagram then

××

×
50N is your force and the acceleration is -9.8m/s^2 due to gravity.
So, you just plug that in.

BUT you know that mass cannot be negative, so you just disregard the negative sign and the mass of the rock is 5.102 grams.