Two kinds of nitrogen fixers are recognized: free-living (non-symbiotic<span>) bacteria, including the cyanobacteria (or blue-green algae) Anabaena and Nostoc and such genera as Azotobacter, Beijerinckia, and Clostridium; and mutualistic (symbiotic) bacteria such as Rhizobium, associated with leguminous plants, and Spirillum </span>
Answer:
D. A positive cation and a negative anion
Explanation:
An ionic compound is defined as the chemical compound formed by the combination of two charged particles or ions held together by electrostatic forces.
An ionic compound is made up of ions, a cation which is a positively charged ion and an anion which is a negatively charged ion. Example of ionic compounds are Lithium Fluoride, Lithium Iodide, and Sodium Bromide.
Hence, the correct answer is "D. A positive cation and a negative anion".
Thanks for points...
But can you type this question.. As it becomes hard to answer if it's in the picture..

The net force acting on the block is ~


So, the Answer in the boxes will be ~

Answer:
Emergent curriculum is an early education approach where teachers design projects unique to a child or group of kids.