How does a thermos keep hot drinks hot?

A: By absorbing radiant energy that might enter the thermos
B: By limiting the amount of thermal energy that flows out of the drink
C: By limiting the amount of cold that flows into the drink
D: By transmitting radiant energy into the thermos

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.

An object resting on a table weighs 100 n. with what force is the object pushing on the table? with what force is the table pushing on the object? explain how you got your answer.

Una carga puntual de 3 x 10-6 c se coloca a 12 cm de una segunda carga puntual de - 1,5 x 10-6 c. calcular la magnitud fuerza eléctrica entre las cargas