Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Class | Part 1 | Part 2 | Part 3 | Part 4 |
| --- | --- | --- | --- | --- |
| 1 | ríða | reið | riðu | riðinn |
| 2a | lúka | lauk | luku | lokinn |
| 2b | frjósa | fraus | frusu | frosinn |
| 3a | binda | batt | bundu | bundinn |
| 3b | verða | varð | urðu | orðinn |
| 4 | bera | bar | báru | borinn |
| 5 | lesa | las | lásu | lesinn |
| 6 | ala | ól | ólu | alinn |
| 7a | heita | hét | hétu | heitinn |
| 7b | hlaupa | hljóp | hljópu | hlaupinn |
| 7c | halda | helt | heldu | haldinn |
| 7d | ráða | réð | réðu | ráðinn |
| 7e | blóta | blét | blétu | blótinn |
Question:
What is Part 1, when Part 3 is "heldu"?
Answer:
halda