Please help me the picture is above, I’ll mark as brainliest.

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.

Pretty sure it's d. heterogeneous is separated by physical properties. 

Each calcium ion has a charge of +2, which can also be written as ca2+. if those ions move out of the neuron and no other ions are moving, the neuron would lose the positive charge associated with those ions and become more negatively charged.

Answer: 1s²  2s²  2p⁶explanation: from the periodic table, we can note that the neutral fluorine  has 9 electrons (symbol is shown in the attached image)therefore, the configuration of neutral fluorine  is: 1s²  2s²  2p⁵now, f⁻  means that the neutral fluorine  gained one extra electron. this means that f⁻  has 10 electrons.the extra electron will occupy the 2p level to make it complete.the configuration now  is: 1s²  2s²  2p⁶comparing between both f and f⁻, we can note that f⁻  has now complete orbitals which means that it is more stable than f based on lewis postulatehope this : )