@jangsunny1030,
Quote:I would like to change the following wish from the present to past.
(I wish that I were going to Switzerland.)
And I come up with two following sentences..
Which one is right?
1.I had gone to Switzerland
2.I had been going to Switzerland.
First, wishes don't have a past, JS. Resulting realities have pasts.
I wish that I were/was going to Switzerland.
First reality - You went to Switzerland.
1. I went to Switzerland.
2. I've been to Switzerland.
3. I had gone to Switzerland [a possible use in more limited situations]
4. I wish I hadn't gone to ... .
Second reality - You didn't go to Switzerland.
1. I didn't go to ... .
2. I haven't been to ... [yet].
3. I wish I had gone to ... .
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Quote:Q2
Ed (says, said) that he plans to go fishing this weekend.
Can I use both of the choices?
Absolutely.
Quote:Q3
I would like to change from direct speech to indirect speech.
In tomorrow's speech, the ambassador will say, "We need to negotiate this treaty."
In tomorrow's speech, the ambassador will say that we (will,would)need to negotiate this treaty.
Can I use both choices?
If by 'both' you mean the addition of either 'will' or 'would', again absolutely you can.
With such a simple sentence, you could even say,
In tomorrow's speech, the ambassador will say that we need to negotiate this treaty.