Answer no 1)
The correct option is A) He did not try to learn it. It was natural.
As Sergei did not put any effort in learning the art of tongue rolling, hence we can assume that this characteristic was found to be naturally present in Sergei. This hence shows that Sergei has acquired the characteristic of tongue rolling through inheritance.
Answer No 2)
We can learn whether other persons in the class have the characteristic of tongue rolling or not by observing them. In the students who can roll their tongue we can conduct a survey asking them whether they tried to learn the trait or did not put any effort to learn tongue rolling. The students who learned the skill by practicing might have acquired the characteristic from learning.
Answer No 3)
We can survey the class for features like eye color, hair color, height, weight. We can ask certain questions in our survey like whether the characteristic can be seen in either the mother, father or other siblings.
Answer:
200 liters of fluoridated drinking water would have to be consumed by as person to reach the toxic level.
Explanation:
Toxic level of fluoride ions = 0.2 g per 70 kg body weight
Concentration of fluoride ions in drinking water = 1 mg/ L = 0.001 g/L
1 mg = 0.001 g
Let the volume of drinking water consumed by person to reach the toxic level of fluoride concentration be V.
For 70 kg body weight 0.2 grams of fluoride ions will be toxic.
200 liters of fluoridated drinking water would have to be consumed by as person to reach the toxic level.
Explanation:
The grey powder of silver ( I ) oxide i.e. Ag₂O breaks down to give a metal called the silver metal and an odorless , colorless gas , which is the oxygen gas .
The balanced chemical reaction is as follows -
Silver oxide -----> Silver + oxygen
Ag₂O ------> Ag (s) + O₂ (g)
The balanced reaction is -
2 Ag₂O (s) ------> 4 Ag (s) + O₂ (g)
