Earthquakes are not easy to predict, but volcanic eruptions have more warning signals and instruments to measure those signals, therefore making them somewhat easier to forecast. the difficulty with predicting volcanic eruptions is a. height of the volcanoes b. number of volcanoes c. shortage of geologists d. cost of monitoring

D. Cost of monitoring

Explanation:

Despite the great concern and commitment of volcanologists, it is still not possible to predict exactly when a volcanic eruption will occur. However, some signs may be indicative of some upcoming activity.  Before an eruption, magma focuses on areas below the volcano, called reservoirs, where it moves producing vibrations, ie small earthquakes. This same movement can cause the slopes of the volcanic cone to collapse. As magma approaches the surface, it releases gases that can be detected in regions near the volcano.

The analysis of these gases allows to verify if there is variation in their quantity and composition. The movement of the magma, however, may not result in eruption. Instead, it can cool and solidify on the subsurface.

Since volcanoes typically come into operation at intervals of hundreds to thousands of years, they are not continuously monitored, even because this practice is costly (which makes monitoring difficult) and the same pattern is not always repeated in different eruptions.

However, when the volcano emits precursor clues, a major catastrophe can be prevented.

the tides are influenced by both the moon and the sun, it's easy to see that when the sun lines up with the moon and the earth, as during a new moon or full moon, the tidal effect is increased. these are known as spring tides, named not for the season, but for the fact that the water "springs" higher than normal. on the other hand, if the sun and the moon are 90 degrees apart in relation to an observer on earth as during the first quarter moon or third quarter moon, then high tides are not as high as they normally would be. this is because despite its greater distance, the sun's mass allows it to exert enough gravitational force on the oceans that it can negate some of the effects of the moon's pull. this phenomenon of lower high tides is called a neap tide. if you need more information on this topic visit moonconnection.com.

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.