During the origin of the eukaryotic cell, it is thought that engulfed bacteria:a. had a mutually beneficial relationship with their hosts initially, but later evolved to become harmful to their hostsb. did not initially have a mutually beneficial relationship with their hosts, but later evolved onec. were always harmful to their hostsd. always had a mutually beneficial relationship with their hosts

b. did not initially have a mutually beneficial relationship with their hosts, but later evolved one

Explanation:

Initially, the host cell engulfed bacteria as food material. It did not have a mutually beneficial relationship with it. However, many engulfed bacteria had several advantages which could also benefit the host cell. For example, some of them could synthesis food material by the process of photosynthesis. The host cell then formed symbiotic relationship with these bacteria. They survived inside the host cell and in return they also supplied the host with prepared food material. Eventually this paved the way for endosymbiosis and origin of many organelles like chloroplast and mitochondria.

here is the answer

water, ice, acids, salts, plants, animals, and changes in temperature are all agents of weathering. weathering is the breaking down or dissolving of rocks and minerals on earths surface. once a rock has been broken down, a process called erosion transports the bits of rock and minerals away.