Answer:

Explanation:
We are asked to find how much of a 40 gram sample remains after 12 years.
Iron-55 has a half-life of 3 years. Therefore, after 12 years, 4 half-lives have been completed.
- 12 years/3 years = 4 half-lives
Every time a half-life is completed, half of the sample's mass decays. Remember we start with a 40 gram sample.
- 1 half- life: 40 g / 2 = 20 g
- 2 half-lives: 20 g / 2= 10 g
- 3 half-lives: 10 g / 2 = 5 g
- 4 half-lives: 5 g / 2 = 2.5 g
There is also a formula that can be used to solve this problem.

Where A₀ is the initial amount, t is the time, and hl is the half-life.
We know 40 grams is the inital amount, 12 years is the time, and 3 years is the halflife.




After 12 years, <u>2.5 grams </u> of Iron-55 will remain.
From the mother through the placenta
Answer: D
Explanation:
The lipopolysaccharides are found in the outer membrane of Gram-negative bacteria. Lipopolysaccharide is complex molecule consisting of a lipid and chains of carbohydrates. They are also called endotoxin, they are the major component of the outer cell membrane. Sugars in the polysaccharide chains of endotoxin confer serologic specificity. They lplay a crucial role in bacteria resistance to antibiotics.
Answer:
: a compound (such as guanosine or adenosine) that consists of a purine or pyrimidine base combined with deoxyribose or ribose and is found especially in DNA or RNA