External stimulus. The rain is something out of your control while you're waiting. Rain is not something you are doing nor is it a response to you waiting for the bus.
Answer:
cell walls, vacuoles, chloroplasts, centriole
Explanation:
Plant cells have cell walls, one large vacuole per cell, and chloroplasts, while animal cells will have a cell membrane only and several smaller vacuoles. Animal cells also have a centriole, which is not found in most plant cells.
Answer:
Option (A)
Explanation:
The Precambrian represents the time period, right from the beginning of the earth to about 540 million years back. It is divided into 3 parts, namely the Hadean, the Archean and the Proterozoic. Throughout this geological time, vast changes have taken place on earth. The first life forms of about 3.8 billion years old, that existed on earth were the simple unicellular organisms, whose traces were only found at some particular places. These organisms were very small and are comprised of soft bodies, so they were affected by the earth's dynamic processes. The organisms in order to get fossilized must contain hard parts. Due to the presence of soft bodies, the organisms were not fossilized and so it took a long time to demarcate that the late Precambrian organisms were animal-like life.
hence, the correct answer is option (A).
