Quick questions on Proton NMR spectroscopy: Singapore A-Level H2 Chemistry

Different chemical environments give different chemical shifts (read from the data-booklet table). Rough guide:

The area under each peak (the integration trace) is proportional to the number of protons in that environment. A ratio of areas $3:2:1$, for example, suggests a $\text{CH}_3$, a $\text{CH}_2$ and one other proton.

A proton's signal is split by the protons on neighbouring carbon atoms, because their spin states slightly alter the local magnetic field. The n+1 rule: a proton with $n$ equivalent neighbouring protons is split into $(n+1)$ peaks:

Protons on O-H and N-H groups can exchange with deuterium when D2O is added. After shaking with D2O, the O-H or N-H peak disappears (the proton is replaced by a non-absorbing deuterium). So a peak that vanishes on adding D2O identifies an exchangeable OH or NH proton.

Predict the splitting pattern of each proton environment in 1,1,2-trichloroethane, $\text{CHCl}_2\text{CH}_2\text{Cl}$. [2 marks]

Explain how you would use D2O to identify the O-H proton in a spectrum. [2 marks]

A spectrum shows integration ratio $9:1$. Suggest a structural feature consistent with the 9-proton peak. [1 mark]