During dehydration synthesis is 42 water molecules were made how many monosaccharides were joined together to make the complex
fast

43 monosaccharides will be joined together to make the complex carbohydrate.

Explanation:

The complex carbohydrates are synthesized by the joining of monosaccharide residues by glycosidic linkages.One glycosidic linkage joins two monosaccharide residues by the elimination of one molecule of water.

  In other words it can be said that elimination of one water molecule joins two monosaccharides.By the same way elimination of 42 molecules of water will result in the joining of 43 monosaccaride residues.

if you listed your answers right then i believe your answer is b.