Several candidates were able to meet the requirements some time ago to appear on the Virginia ballot. Several of those have subsequently decided not to continue their campaigns. It is your responsibility as a voter to know whether your choice is still seriously expecting to win delegates from Virginia. Of course you may vote for any choice on the ballot even if you do not expect that candidate to win. Such a vote can be interpreted as a political comment and be meaningful in that way. You can tell who is still running by consulting their public comments available in the media including the internet and especially their own web sites.
The most immediate source of official information is the Virginia Department of Elections. https://vote.elections.virginia.gov/VoterInformation They will have current information on where you need to vote. The deadline to register to vote in the primaries (to determine party nominees) on Super Tuesday has passed. You must be already registered to vote then. If you have voted in Virginia before, your registration is likely still valid since it does not automatically expire. You can find out if it's still valid on the Department of Elections web site.
The deadline to register to vote in the general election (to determine who is president) is October 17, 2016. That's 22 days before the election on November 8, 2016.
The political parties each have web sites with helpful information, as do the individual candidates.
Opinions on whether Donald Trump can win against Hillary Clinton in the general election appear to vary considerably. He would likely need significant developments in his campaign to even come close. It would not be unusual for a candidate to vary his strategy after obtaining the nomination, if he does, and before the general election. Perhaps his supporters are keeping options open the public has yet to see. Counting on those is not recommended.
Ted Cruz and Marco Rubio are each highly skilled debaters. They will likely be important leaders in the Republican Party in the future even if they do not succeed in getting the nomination or the presidency. They are likely too young to win against Hillary Clinton, but their positions on various issues can mature quickly with all the help they're getting.
Ben Carson is in an awkward position to deliver a message of reducing the role of government in managing health care, but he is perfectly capable of getting that message through.
Hillary Clinton might get many votes simply because she is a woman, but there is no law against that. Her experience in government is formidable despite the many questions surrounding it.
Bernie Sanders does not appear strongly in favor of capitalism. A political candidate describing himself as "socialist" has been unusual in this country. People who still think it should be probably won't vote for Sanders, certainly not in the general election anyway because many in the United States of America have regarded the country as a model of well tempered capitalism.
None of the candidates, especially those still leading the game, are "weak" on national security or defense, though several are surprisingly and disturbingly inexperienced.
Guiding an economy that hasn't been agrarian in about a century through the narrowing paths left by dwindling resources is no simple task. Although it is not something the young should do, it is something they will have to do one day.