The outer membrane of the nuclear envelope is continuous with the membrane of the and is usually covered with attached ribosomes

The endoplasmic reticulum is in continuity with the outer membrane of the nuclear envelope. The ribosomes are attached to these endoplasmic reticulum. Such endoplasmic reticulum with the ribosomes attached to the outer membrane is known as rough endoplasmic reticulum or RER. RER is important in the synthesis as well as processing and transportation of the proteins.

Hence, the blank can be filled with 'endoplasmic reticulum'.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).

allowed for the prediction of the properties of missing elements.