When going through flashcards and asking "What's this?" make the question real by putting the flashcards on your head so that you cannot see the cards.
Teachers questions, like their tests, are traps.
John Holt How Children Fail
I think testing children should be consigned to the dustbin of history. Certainly testing does nothing to contribute to a warm, relaxed environment. For most children it does nothing to encourage participation. Testing does not encourage risk taking. It can lead children to focus upon producing "right answers" rather than on actual learning. Testing tends to prepare children for failure.
All too often teachers create tests without even realising it. Because a teacher has a position of authority any question the teacher asks can easily become a test. Showing a flashcard and ask children, "What's this?" is a kind of test, that is, unless the teacher turns it into a kind of game by making the question real.
When I review flashcards I put them on my head so it becomes absolutely clear that I cannot see the card. I can look at the card after hearing an answer. Or several answers. It's much more natural to ask for an answer to be confirmed when the question is real. So I can ask the whole group and then after someone calls out an anser confirm that answer by following up and asking individually.
If the children have made a mistake and misindentified the card I have a couple of options. I can take a mental note to look at the item again at a latter date, or I can "discover" that something is "different" and that the answer given is "not" the answer on the card. With this in mind it is useful to use flashcards with an image on one side and the word on the other.
Mix in some "new" cards with those that are being reviewed. In addition to serving as a basis to introduce "We don't know!"/"I Idon't know!" this creates a chance for genuine communication. The teacher can ask questions, guess the answer and then look at the card for confirmation. This can be a game in its own right. How many cards can the children help the teacher to identify correctly?