which is a counterexample to the following conjecture?
the sum of the sequence 1+2+2- + +2, where n is a whole number, is always a prime number.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

1.solid

2.carbon dioxide

3.helium

frequency, z, and the collision density, z, in carbon dioxide (co2), r 180 pm at 30 °c and 120 kpa

i think it's letter a.