identify the sentence that shows a cause-and-effect relationship.

For the best results, be sure to complete the entire project.
Some plants grow best in the spring, while others blossom in the summer.
As soon as I completed all of my work, I began playing video games.
Since I lost my wallet, I was unable to pay for my gum at the checkout.

Since I lost my wallet, I was unable to pay for my gum at the checkout.

Since I lost my wallet, I was unable to pay for my gum at the checkout.

The sentence that shows a cause-and-effect relationship is: "Since I lost my wallet, I was unable to pay for my gum at the checkout."

This sentence demonstrates a cause-and-effect relationship because losing the wallet is the cause which leads to the effect of being unable to pay for the gum at the checkout.