If MFJ both must have earned income. This is from IRS: "You may be able to claim the child and dependent care credit if you paid expenses for the care of a qualifying individual to enable you (and your spouse, if filing a joint return) to work or actively look for work". See link.

 https://www.irs.gov/publications/p503

Terry is right. Look in reference material like quickfinder or taxbook or U.S. Master tax guide and you will find the relevant information. You can make a copy of that and then put it in their file.

Is the wife a full time student or disabled? 

When all else fails - read the instructions