Which of the following statements about carbon cycle is not true :-

Options

A. 71% carbon is found dissolved in oceons
B. Atmosphere only contains about 1% of total global carbon
C. Annually `4 xx 10^(18) Kg` of carbon is fixed in the biosphere through photosynthesis
D. Carbon constitute 49% of dry weight of organism and is next to water

Answer

To determine which statement about the carbon cycle is not true, let's analyze each statement one by one:

1. **Statement 1**: "71% carbon only found dissolved in oceans."
- This statement is misleading. While a significant amount of carbon is indeed dissolved in the oceans, it is not accurate to say that 71% of carbon is only found there. The carbon cycle involves various reservoirs including the atmosphere, biosphere, and sediments.

2. **Statement 2**: "The atmosphere only contains about 1% of total global carbon."
- This statement is also misleading. The atmosphere does contain a smaller fraction of the total carbon compared to oceans and terrestrial ecosystems, but it is not accurate to say it is only 1%. The atmospheric carbon is a significant part of the carbon cycle.

3. **Statement 3**: "4 x 10^18 kg of carbon is fixed in the biosphere through photosynthesis."
- This statement is generally considered accurate. The amount of carbon fixed through photosynthesis in the biosphere is indeed in the range of several hundred billion tons, which can be approximated as 4 x 10^18 kg.

4. **Statement 4**: "Carbon constitutes 49% of the dry weight of the organism and is next to water."
- This statement is also accurate. Carbon is a major component of organic molecules and constitutes a significant percentage of the dry weight of living organisms.

After analyzing all statements, we can conclude that the statements about the percentage of carbon in the atmosphere and the percentage found in oceans are misleading. However, the statement that is most clearly not true is:

**Conclusion**: The first statement, "71% carbon only found dissolved in oceans," is not true.