1. Paying attention to "linking", listen carefully.

2. Mark 'linking' where two words are pronounced as a linking sound.

3. Mark 'linking' between/under two words which are pronounced as a linking sound.
(What about under instead of between?)

4. Put 'the linking mark' where two words are pronounced as a linking sound.

5. Put linking between and under the two words.

ex) I like her.
(Like her is pronounced as a linking sound. So you should put 'linking' between and under the two words.)

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Are the expressions above correct?
According to your correction, I changed and added some more expressions. Would you check them, please? Writeacher?

Could anybody answer the questions?

The expressions you provided are not quite accurate or clear. Here's a revised version with explanations on how to mark the linking sound:

1. Pay attention to "linking" when two words are pronounced as a continuous sound.

2. Mark "linking" where two words are pronounced as a continuous sound without a pause. (For example, "sister" and "in" in the phrase "his sister-in-law.")

3. Mark "linking" between or under two words when they are pronounced as a continuous sound. ("Between" is more commonly used, but "under" is also acceptable in some cases.)

4. Put "the linking mark" where two words are pronounced as a continuous sound. (Be sure to specify the type of mark you are using.)

5. Use "linking" to indicate that two words are pronounced as a continuous sound, placing it between or under the two words.

Example: In the phrase "I like her," the words "like" and "her" are pronounced smoothly together as a linking sound. To mark this, you can use "linking" between the words or place it under them.