Goggles, a lab coat, chemical gloves, and close- toed shoes
If you travel 30 miles somewhere and then come home again your distance is 60 miles. Your displacement is 0 because it is the ending position minus the beginning position, which are the same place (home). In other words, displacement is a vector and distance is a scalar.
If one bulb goes out then all the others won't light up because electricity will be cut off. It's a disadvantage because in a parallel circuit if one bulb burns out all the others will still be on because they won't be affected. I hope I've helped you ☺