The answer is SHIT or CRAP.
Most native speakers of English would automatically finish the line as "What a lot of shit!" or "What a lot of crap!" One might also say, "What a load of crap/shit!" It's said when you don't believe something. It's similar to saying that something is bullshit. Both shit and crap are considered rather vulgar, so one could substitute "What a lot of baloney!" or "That's baloney!" Baloney refers to a cheap kind of sandwich meat. You could say baloney without offending anyone.
Crap means shit, but the word has an interesting history. In many parts of the world even today, shit stays where it is put, unless it is carted away to be used for manure (natural fertilizer from animals, including humans). Outhouses are built over deep holes dug in the ground. However, over 100 years ago someone came up with the idea of a flush toilet: when one pulled a rope, water rushed forth and took the excrement away. That man's name was Thomas Crapper, and the first commercially produced flush toilet was known as a crapper.
But then something happened that is called in linguistics semantic shift. The word crapper changed from referring to the name of the new invention to the activity performed with this invention. Thus one could imagine people first saying, "I'm going to the crapper" and then somewhat later saying "I'm going to take a crap" perhaps on the analogy of "I'm going to take a shit" which was already in the English language. Thus Mr. Crapper's name has gone down in history, but perhaps somewhat more humbly that he might have wished.