Pine trees do not have flowers. What structure do they have that servers the same purpose?

1. Needles

   No. Pine needles are a kind of leaf. They are not used for reproduction.

2. Cones

   Yes! Pine cones produce pollen and seeds, just as flowers do in flowering plants.

3. Fruit

   No. Fruit are used for dispersing seeds, not for pollination.

4. Buds

   No. Pine tree buds produce needles. They are not involved in reproduction.

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None of these layers have been turned upside down. Based on the Law of Superposition, which layer is the oldest?

1. A

   No. Layer A is on top of layer B, so it is younger than layer B. That means that it is not the oldest.

2. B

   No. If you look at layer B, it is on top of layer C, which means that it is younger than layer C. B is not the oldest.

3. C

   No. Look closely at the top part of layer C. The top part of layer C is on top of part of layer D. That tells us that layer C is younger than layer D.

4. D

   Yes! This one is a bit tricky, because of the way the rocks were formed. Layer D formed first, as a flat, horizontal layer. Erosion weathered the left part of D away, forming a sloping hillside. Image the photo with layers A, B, and C erased, and it looks like a sloping hillside.

   Next, a nearby volcano erupted, spewing out lots of volcanic ash. The ash covered the hillside, forming layer C.

   Next, lava from the volcano flowed down over the ash, forming layer B.

   Later, the volcano erupted again, depositing another layer of volcanic ash to form layer A. After that, layer A was covered by another layer of lava, and then another layer of volcanic ash.

   So A is the youngest, followed by B, then C, and D is the oldest.

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