In earlier plays through Civ5 I've been able to set a city's production to Research, so I know it's possible, but I've not determined what it is that enables that (in my current game, Research isn't an option from the production menu for any of the cities). What's required (a particular tech, I'm assuming) to make that available?
Researching Education allows the conversion of Production to Research. (i.e. allows cities to "build" beakers)
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In Starcraft 2's single player campaign, two new research options unlock for every 5 Zerg/Protoss research points recovered, up to the maximum of 25 research points per race.
What are the pros and cons of the choices available at each tier for Zerg and Protoss research? Are there particular combinations that work particularly well together?
There are three that come to mind that I strongly feel have a better alternative.
"Build 2 SCVs at once" or "Vespene Geysers do not require SCVs for gathering"
Choose build 2 SCVs at once. Doubling the rate at which you build SCVs has an exponential impact on your economy. The 3 or 6 SCVs you lose to mining gas is negligible compared to how much faster you can get your economy going. Especially in the last mission. I completed it on Brutal, and was non-stop building SCVs for gathering minerals and repairing units. Not having to gather gas is really only a significant help in one of the campaign missions.
"Tech-reactors" or "Drop pods"
Choose Tech reactors. Not only do Tech-reactors allows you to spend fewer resources on structures, and more on units, but they also increase your unit production rate. The drop-pod ability is late in the game, and faster deployment for ONLY Barracks units is not as helpful as faster and cheaper production.
"+25% Geyser allocation" or "Instant Supply Depots"
If you are good at keeping track of your supply count, choose the +25%. While calling down Supply Depots instantly has its uses when you are trying to create a wall-in. If you can keep track of your supply count, there's no reason to miss out on +25% gas allocation.
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