Which weather componet could cause a drop in air pressure I need it know please

Volcanic irruption is most likely to be violent when a) volcanoes near to the sea b) the neck of the volcano is sealed by a plug c) the lava is viscous d) the lava reaches the surface through a fissure e) the volcano is on the ocean floor

What can you learn about precipitation levels in south america from this map? brazil is experiencing a drought. it rains more in higher altitudes. peru received the highest level of rain. venezuela got less than 25 cm of rain. 

Which of the following is an example of relocation diffusion