Certain antibiotics are no longer effective against the bacteria that they used to kill. Which of the following best explains why certain antibiotics are no longer effective? The number of bacteria is now greater than what the antibiotic can kill

The antibiotic has become weaker over time

Bacteria that were resistant to the antibiotic survived to reproduce

Changes in the environment made the antibiotic ineffective

Four point charges each having charge q are located at the corners of a square having sides of length a. find symbolic expressions for the following. (a) the total electric potential at the center of the square due to the four charges (use any variable or symbol stated above along with the following as necessary: ke.) vtotal= (b) the work required to bring a fifth charge p from infinity to the center of the square (use any variable or symbol stated above along with the following as necessary: w=