Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Hinge Joint. The knee joint is a hinge joint. Like a door hinge, a hinge joint allows backward and forward movement. Answer: hinge joint
[EX A]: What type of joint is the knee joint?

[EX Q]: Passage: The electron cloud of a helium atom contains two electrons, which can normally be expected to be equally distributed spatially around the nucleus. However, at any given moment the electron distribution may be uneven, resulting in an instantaneous dipole. This weak and temporary dipole subsequently influences neighboring helium atoms through electrostatic attraction and repulsion. It induces a dipole on nearby helium atoms (see Figure below ). Answer: an instantaneous dipole
[EX A]: A weak and temporary dipole that influences nearby atoms through electrostatic attraction and repulsion is known as what?

[EX Q]: Passage: Sperm are male gametes, or reproductive cells. Sperm form when certain cells in the male reproductive system divide by meiosis to form haploid cells. Being haploid means they have half the number of chromosomes of other cells in the body. An adult male may produce millions of sperm each day!. Answer: reproductive
[EX A]:
What type of cells are gametes?