Which one of the following is a double-displacement reaction?
~there can be more then one answer~

a. 2h2 (g) + o2 (g) → 2h2o (g)
b. 2h2o (l) → 2h2 (g) + o2 (g)
c. naoh (aq) + hcl (aq) → nacl (aq) + hoh (l)
d. cu (s) + 2agno3 (aq) → cu(no3)2 (aq) + 2ag (s)

Atruck driver is attempting to deliver some furniture. first, he travels 8 km east, and then he turns around and travels 3 km west. finally, he turns again and travels 13 km to his destination. what is the drivers distance

The weights of bags filled by a machine are normally distributed with a standard deviation of 0.05 kilograms and a mean that can be set by the operator. at what level should the mean weight be set if it required that only 1% of the bags weigh less than 9.5 kilograms? round the answer to 2 decimal places.

It may seem strange that the selected velocity does not depend on either the mass or the charge of the particle. (for example, would the velocity of a neutral particle be selected by passage through this device? ) the explanation of this is that the mass and the charge control the resolution of the device--particles with the wrong velocity will be accelerated away from the straight line and will not pass through the exit slit. if the acceleration depends strongly on the velocity, then particles with just slightly wrong velocities will feel a substantial transverse acceleration and will not exit the selector. because the acc