One reason that we observe a tight link between consumption and disposable income is:

There are strong theoretical reasons to expect that changes in wealth are responsible for changes in consumption. Nonetheless, one reason that we observe a tight link between consumption and disposable income is:
(A) Credit rationing which changes the intertemporal budget constraint for borrowers.
(B) Households attempt to smooth their consumption.
(C) Household saving provides a buffer between income and expenditure.
(D) Ricardian equivalence

The answer is: (B) Households attempt to smooth their consumption.