Other.
Many of those options fit to some degree, but not to the same degree.
Weather and terrain manipulation should be a fairly obvious staple of druids. Helping the crops, mitigating droughts and floods/monsoons, lessening the severity of storms (or calling on storms to afflict enemy settlements), clearing away landslides, etc. This kind of magic is really important to a proper druid-type class.
Animal-related magic should also be a fairly obvious part of druidism, but not the primary aspect of druidism. Nature isn't just about the stuff that walks, crawls, swims, and flies. It's about the plants, germs, land, air, water, sunlight, and other natural forces, too. Animal magic is a secondary or tertiary aspect of druidism, definitely not the most important.
Plant-related and fey-related magic are obvious aspects of druidism and should be fairly important to the concept. If anyone is going to be an emissary to the fey realms or fey creatures, it's the druid. If anyone's going to help the crops, restore the wildfire-scorched forest, or take care of a desert oasis, it's the druid. These are important aspects of druidism.
Spirit magic or similar matters would be a significant aspect of traditional, historical druids, but in D&D it may be less significant. The druid may venerate Obad-Hai, Silvanus, or any other nature-deity of choice, but is more likely to pay respects to all nature deities and try to keep all of them (or at least their favorite ones) placated. Druids are more about taking care of nature and serving nature as a whole, than about running errands for this deity or that deity like some simpering cleric. Nature itself will give of itself if the druid only does the same for nature, in a mutually beneficial relationship. Still, druids may be significant intermediaries between nature spirits and mortals, or between nature deities and mortals, so spirit magic should be a secondary or tertiary aspect of druids. In 3E this takes the form of Commune with Nature, Summon Nature's Ally, Scrying, and similar spells stemming from the druid's minor relationship with nature spirits or nature deities.
Elemental magic is not so directly obvious as a druidic aspect; it is not so strongly tied to the druid class' historical/religious roots, but it is something that you'd expect in D&D. So I'd expect D&D druids to have a reasonably strong connection to the elements, but not as their primary focus. Nature is more about the harmonious combination of stuff in the world than about the individual forces that contribute. Elementalism is a secondary or minor aspect of druidism, but hardly a major focus of it; druids would focus more on the relationship between elemental forces and other natural things, like plants and animals, which basically means utilizing the weather, climate, and terrain that comes about from elemental processes.
Shapeshifting? Well, it has some traditional precedent I think, but it's certainly not something that fits as a primary focus for druids. It's something you might expect a druid to do, hiding in the guise of animals, plants, rocks, or other people, but not something you'd expect them to do all the time. At best it should be secondary or tertiary in a druid's set of abilities, at worst it could be ditched altogether without any conceptual problems.
So, overall I'd put them in order of significance to a druid class as:
1 - fey, terrain, and weather magic
2 - animal, plant, and spirit magic
3 - elemental magic and shapeshifting
