Given below is a simplified model of phosphorus cycling in a terrestrial ecosystem with four blanks (A-D). Identify the blanks.

• A

  A- Rock minerals; B- Detritus; C- Litter fall; D- Producers

• B

  A- Litter fall; B- Producers; C- Rock minerals; D- Detritus

• C

  A- Detritus; B- Rock minerals; C- Producers; D- Litter fall

• D

  A- Producers; B- Litter fall; C- Rock minerals; D- Detritus