The bright light emission spectrums below are seen through a spectroscope. The unknown sample is a mixture of the observed gases.

5 rectangles labeled gas W, gas X, gas Y, gas Z and unknown sample. Gas W has 2 black lines left of center and 2 black lines close together right of center. Gas X has two black lines on the far left one on the far right and one on either side of center. Gas Y has one black line on either side of the center and one black line further right. Gas Z has one black line on the far left, one in the center and 2 on the right. The unknown sample has one black line on the far left, one in the center, one on either side of center and 2 on the right.

Which gases are found in the unknown sample?

gases W and Z
gases X and Y
gases W and Y
gases Z and Y

coil wire, increase current, put iron inside the coil

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.