Will the light from two very close stars produce an interference pattern?
a. yes; intense light from two nearby stars creates very obvious interference patterns.
b. no; the light from two different incandescent objects is not coherent, and is emitted in a range of frequencies.
c. no; the light is too intense to produce a discernable interference pattern, it gets washed out.
d. yes; if they are very close to each other, the light has a large overlapping area and in this area you will see interference.

You have two photos of a person walking. one shows the person at the corner of third and main streets, the other shows the person at the corner of tenth and main streets. there are lampposts at every corner in this town, and the first picture shows it to be 10: 32: 00 exactly. the second picture shows it to be 10: 49: 30. you know three facts: (1) all of the clocks are synchronized; (2) there are exactly 12 equal-sized blocks per kilometer in this town; and (3) the streets that cross main in this area are numbered consecutively, with no interruptions. what is the person’s average speed in kilometers per hour?