What's wrong with my code?

Right now, you're declaring the sentence variable as a string that contains -

<h1>noun + ' verb + ' adjective + ' ceviche. </h1>

If you declare a variable, and the content of the variable is between a set of quotation marks, you're telling the interpreter that you're declaring a string, and the information within said quotation marks is the content of the string.

In order to add variables to the mix, you can concatenate them. To do that, we put our HTML elements within quotation marks, along with any words or formatting (such as whitespace or punctuation) we would want, while the variables would be left outside of quotation marks so that they are read as variables, and join each piece with plus signs. So, something like this.

var sentence = "<h1>" + noun + " " + verb + " " + adjective +  " ceviche. </h1>";

You'll learn this soon, but if you want to know a way that's even quicker to write and, IMO, easier to read, you could use a template literal. You'll learn about these in the near future, but our sentence variable from before would basically just look like this.

var sentence = `<h1>${noun} ${verb} ${adjective} ceviche.</h2>`;

All we do here is wrap everything in a set of backticks ( ` ), wrap the content between our HTML tags, write it out like a normal sentence, but for each variable, we write it with the dollar sign and curly braces, so ${variableName}.

Hope that helps, keep up the good work.