Consider the following statements $(A-D)$:
$(A)$ Heterocysts are important sites for nitrogen fixation in $\text{BGA}$.
$(B)$ Cell wall of diatoms is indestructible due to presence of calcium carbonate.
$(C)$ In fungi,the cell wall is made up of chitin.
$(D)$ Algae show isogamous,anisogamous,and oogamous types of sexual reproduction.
How many of the above statement$(s)$ is/are not correct?

• A
  $1$
• B
  $2$
• C
  $3$
• D
  $4$