But, 4 is possible.

After Salinas v Texas, you must positively assert that you are exercising your right to silence, not simply remain silent.

The prosecutor in a murder trial argued, at trial, that silence of the defendant (during police questioning) was evidence of his guilt. The supreme court in Salinas v Texas allowed this.

* The defendant also selectively answered some questions, so perhaps there is nuance, but to be safe, a positive assertion of right to remain silent seems prudent.

IANAL, and would love if an actual lawyer would comment on this.