Final answer:
To find out which two cities have the greatest combined annual rainfall, Mumbai with its monsoon season and Tokyo with significant rainfall is the likely pair. London has moderate rainfall and Sydney's is comparatively lower. Cities like Delhi and Lagos are projected to have decreased precipitation in the future.
Step-by-step explanation:
The question is asking for a comparison of the combined typical annual rainfall totals of Tokyo and Sydney versus London and Mumbai. Based on global rainfall data, Mumbai experiences a very high amount of rainfall due to the monsoon season, while London's rainfall is moderate. Tokyo also has a significant amount of rainfall, whereas Sydney's is comparatively less. To determine which two cities have the greatest combined rainfall for a typical year, we would look at climate statistics for these cities. Given that Mumbai has one of the highest rainfalls due to monsoon seasons and that Tokyo also receives significant rainfall, it is likely that the combination of Mumbai and any other city among the options would result in the highest combined rainfall.
Although specific data for the annual precipitation of these cities is not provided in the reference information, it is known that the listed cities like Delhi, Lagos, and others are expected to face moderate to severe precipitation decreases and potential water supply challenges by the end of the 21st century, which is a separate concern from the question at hand.