建造自己的房子是一项重大的任务。

Building your own house is a major ___undertaking.

虽然这样的任务非常可取，但我想指出可能存在缺点。

While such an ___undertaking is most advisable, I should like to point out that there may be drawbacks.

组织这次国际会议被证明是一项复杂的任务。

Organising the international conference proved to be a complex ___undertaking.