Problem diagram.
Black's response to the marked stone?

Source:
American Go Journal, Vol. 22, No. 4, pp. 29-30
Keshi and Uchikomi, Kaoru Iwamoto 9 dan

Solution follows    (or click here to download SGF)

Correct.
Just like the similar problem from last week, every go player must know what to do if White makes the contact play after Black invades. When Black has outside help, Black simply pushes out with 1. When White presses with 2, Black hanes with 3. White may decide to block at the bottom with 4. Through 7, Black's invasion has been clearly successful.

Dozens of variations exist depending on the surrounding stones, but the simple themes here are common to many of those positions.

White variation.
White can also connect at 4, but after 5, Black has again been successful at invading and connecting out.

White variation.
White can try to stop Black from connecting by standing up with 2. But Black can simply push through with 3. After White blocks, Black will connect out with 5 anyway.

For example, if White persists with 6, the sequence to Black 15 is a simple one-way street. Black wins the semeai.

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