Table:
|  |  |  | Number of share options |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Name of director | Date of grant | As at 1 January 2019 | Granted during the year | Exercised during the year | As at 31 December 2019 | Exercise price | Exercise period |
|  |  |  |  |  |  | HKD |  |
| Lau Chi Ping Martin | 25 March 2014 | 5,000,000 | - | - | 5,000,000 | 114.52 | 25 March 2015 to 24 March 2021 (Note 2) |
|  | 21 March 2016 | 3,750,000 | - | - | 3,750,000 | 158.10 | 21 March 2017 to 20 March 2023 (Note 2) |
|  | 24 March 2017 | 5,250,000 | - | - | 5,250,000 | 225.44 | 24 March 2018 to 23 March 2024 (Note 2) |
|  | 9 April 2018 | 3,215,800 | - | - | 3,215,800 | 410.00 | 9 April 2019 to 8 April 2025 (Note 2) |
|  | 4 April 2019 | - | 3,506,580 (Note 3) | - | 3,506,580 | 376.00 | 4 April 2020 to 3 April 2026 (Note 2) |
|  | Total: | 17,215,800 | 3,506,580 | - | 20,722,380 |  |  |
Paragraphs:
The Company has adopted five share option schemes, namely, the Pre-IPO Option Scheme, the Post-IPO Option Scheme I, the Post-IPO Option Scheme II, the Post-IPO Option Scheme III and the Post-IPO Option Scheme IV. The Pre-IPO Option Scheme, the Post-IPO Option Scheme I, the Post-IPO Option Scheme II and the Post-IPO Option Scheme III expired on 31 December 2011, 23 March 2014, 16 May 2017 and 13 May 2019 respectively.
As at 31 December 2019, there were a total of 20,722,380 outstanding share options granted to a director of the Company, details of which are as follows:
1. For options granted with exercisable date determined based on the grant date of options, the first 20% of the total options can be exercised 1 year after the grant date, and each 20% of the total options will become exercisable in each subsequent year.
2. For options granted with exercisable date determined based on the grant date of options, the first 25% of the total options can be exercised 1 year after the grant date, and each 25% of the total options will become exercisable in each subsequent year.
3. The closing price immediately before the date on which the options were granted on 4 April 2019 was HKD378.
4. No options were cancelled or lapsed during the year.
Question:
When did the Pre-IPO Option Scheme expire?
Answer: 31 December 2011